Economics and Human Biology 12 (2014) 140–152

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Economics and Human Biology journal homepage: http://www.elsevier.com/locate/ehb

Racial differences in the influence of female adolescents’ body size on dating and sex Mir M. Ali a,1, John A. Rizzo b,c,*, Aliaksandr Amialchuk d,2, Frank Heiland e,3 a

Analysis & Services Research Branch, Substance Abuse & Mental Health Services Administration, Rockville, MD 20857, USA Department of Economics, State University of New York at Stony Brook, Stony Brook, NY 11794, USA c Department of Preventive Medicine, State University of New York at Stony Brook, Stony Brook, NY 11794, USA d Department of Economics, University of Toledo, Toledo, OH 43606-3390, USA e CUNY Institute of Demographic Research, School of Public Affairs, Baruch College, New York, NY 10010, USA b

A R T I C L E I N F O

A B S T R A C T

Article history: Received 2 April 2012 Received in revised form 11 November 2013 Accepted 20 November 2013 Available online 1 December 2013

This paper investigates the effect of body size on dating and sexual experiences of white (non-Hispanic) and African American (non-Hispanic) female adolescents. Using data from Add-Health, we estimate the effects of obesity and BMI z-score on the probability of having been involved in a romantic relationship, having ever been touched in the genital area in a sexual way, and having ever engaged in sexual intercourse. We find that obese white teenage girls are less likely to have been in a romantic relationship compared to their nonobese counterparts. In addition, obese white girls are less likely to ever have had sex (intercourse) or to ever have been intimate. There are no systematic differences in relationship experiences and sexual behaviors between obese and non-obese black girls. Overall, the estimated relationships are very robust to common environmental influences at the school-level and to the inclusion of proxies for low self-esteem, attitudes toward sex and interviewer assessment of appearance and personality. Instrumental variables estimates and estimates from models with lagged weight status confirm the overall patterns. ß 2013 Published by Elsevier B.V.

JEL classification: I12 J10 Z13 Keywords: Obesity Body image Adolescence Sexual behavior National Longitudinal Survey of Adolescent Health

1. Introduction Body size is a prominent aspect of appearance, and as such it is subject to esthetic assessment. A physical appearance that is deemed attractive by others is an asset that is valuable in many situations of human interactions such as in the labor market (Hamermesh and Biddle, 1994;

* Corresponding author at: Department of Preventive Medicine, State University of New York at Stony Brook, Stony Brook, NY 11794, USA. Tel.: +1 631 741 8539; fax: +1 631 444 3480. E-mail addresses: [email protected] (M.M. Ali), [email protected] (J.A. Rizzo), [email protected] (A. Amialchuk), [email protected] (F. Heiland). 1 Tel.: +1 240 276 1336; fax: +1 240 276 1260. 2 Tel.: +1 419 530 5147; fax: +1 419 530 7844. 3 Tel.: +1 646 660 6700; fax: +1 646 660 6701. 1570-677X/$ – see front matter ß 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.ehb.2013.11.001

Mobius and Rosenblat, 2006), romantic relationships (Carmalt et al., 2008; Cawley et al., 2006; Pearce et al., 2002), and, more broadly, situations of face-to-face interaction and exchange (Mulford et al., 1998; Ali et al., 2012). How individuals value physical attributes such as body size depends on their preferences. Social scientists believe that body size preferences, in turn, reflect a complex set of factors, including socio-cultural influences such as body size ideals (‘‘beauty norms’’) and attitudes toward overweight and obese individuals (‘‘stigmatization’’), which may vary independently of body size ideals. Stigmatization of overweight and obese people is a fairly well-known phenomenon. Relative to non-obese subjects, obese individuals are viewed as less attractive (Ali et al., 2013), less intelligent, and less industrious,

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among other qualities.4 Furthermore, obesity has been linked to low self-esteem and elevated risk of depression among women (Ali et al., 2010; Graham and Felton, 2005; Ross, 1994). Discrimination on the basis of body weight may contribute to observed obesity-related wage, jobstatus, and marriage-market penalties (see, for example, Averett and Korenman, 1996, 1999; Cawley, 2004; Baum and Ford, 2004; Conley and Glauber, 2005; Morris, 2007; Mukhopadhyay, 2008). Recent research using Body Mass Index (BMI) as a proxy for physical attractiveness has also documented relationship and marriage market penalties among individuals with higher BMI (Chiappori et al., 2012; Oreffice and Quintana, 2010). Specifically, Oreffice and Quintana (2010) show that heavier women are more likely to end up with husbands of lower socioeconomic and physical status, i.e., with husbands who are poor, less educated and short in stature. The range of body sizes considered attractive may differ across socio-cultural groups and as a result, can deviate from the standard implied by official classifications of what constitutes a ‘‘normal’’ or ‘‘healthy’’ body size.5 In particular, there are reasons to suspect that the consequences of high BMI and obesity may vary across black and white females as a result of cultural differences in ideal body size (Furnham and Alibhai, 1983; Hebl and Heatherton, 1998; Spitzer et al., 1999), obesity stigma, and related identity perceptions. For example, Cawley (2004) finds wage penalties associated with obesity among white women, but not among black women. Averett and Korenman (1996, 1999) document sizeable negative relationships between obesity status and white women’s marriage prospects and spousal incomes, but find little evidence of a similar link for black women. Moreover, black (nonHispanic) women have been found to be less likely than women in other racial and ethnic groups to perceive themselves as overweight, even after controlling for objective weight status (see Molloy and Herzberger, 1998; Burke and Heiland, 2008; Burke et al., 2010). Appearance and body weight are known to play an important role during adolescence. Preoccupation with body image, especially the experience of what physique ‘‘others’’ consider as ideal, is a central theme, especially for girls, during that time. Milestone physical and psychological developments set the stage for interests and activities that increasingly take teenagers outside the family home and out of the immediate control of their parents. Opportunities to experience romantic relationships and physical intimacy abound as the social environment expands. In turn, adolescents, especially girls, are sub-

4 Stigmatization has been found to take various forms, including social exclusion, public ridicule, and mistreatment by doctors. Studies of the stigmatization of obesity include Rand and MacGregor (1990), Hebl and Heatherton (1998), Puhl and Brownell (2001), and Ali et al. (2012), among many others. 5 For evidence on socio-cultural differences in weight norms, see, for example, Burke and Heiland (2008), Graham and Felton (2005), Voracek and Fisher (2002), Stearns (1997), and Garner et al. (1980), among others. 6 For example, Ali et al. (2011a) and Maximova et al. (2008) find that young people’s perceptions of weight and being overweight depend on the weight of their friends, underlining the importance of peers in shaping one’s view of physical attributes during adolescence.

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jected to unfamiliar levels of scrutiny by peers with respect to their (changing) physical attributes, and experience greater awareness of body image.6 Romantic relationships and sexuality are important aspects of the adolescent social experience and studies have reported that most adolescent girls report a desire for romantic involvement (Halpern et al., 1999). In addition, romantic relationships and sexual behavior are integral parts of the pubertal accommodation process among female adolescents – a time period in the life course where the body goes through a significant transformation in terms of appearance and reproductive maturity (Feiring, 1999; Coates, 1999). Given the importance of romantic and intimate relationship experiences among adolescents, and the steady rise in obesity rates among that age group, the relationship between body weight and sexual behavior and romantic relationships is an important, though understudied, area of social science research. In addition to policies dealing with such negative phenomena as adolescent sex, pregnancies, and depression, uncovering the determinants of adolescent dating and sexual behaviors will inform a wider range of policies dealing with stigmatization and discrimination against obese individuals, later-in-life labor market and health outcomes. Uncovering differential impacts by race of body weight on romantic and sexual relationships will make policy interventions more efficient by focusing resources on specific demographic groups. This is especially important given the pronounced differences between races in many of these outcomes. This paper investigates the relationship between body size and the dating and sexual experiences of white (nonHispanic) and African-American (non-Hispanic) female adolescents. Socio-cultural differences in the effects of female body size on adolescents’ intimate relationships have received little attention to date. Averett et al. (2013), Cawley et al. (2006), and Sabia and Rees (2011b) report evidence of a negative relationship between body weight and sexual behaviors using samples of female adolescents. To the best of our knowledge, the present study provides the first estimates of race-specific effects of body weight on a rich set of measures of relationship experiences and intimate behaviors. Using large, nationally representative samples of adolescents, we estimate the effects of obesity and BMI z-scores on the probability of being in a romantic relationship, having sexual intercourse and being touched in the genital area in a sexual way (or being intimate). Understanding the determinants of dating and sexual behaviors of adolescents is of considerable interest to researchers, policy makers, and parents. This likely reflects concerns over the disease and pregnancy risks that sexually active teenagers face and the potential long-term adverse consequences for health and well-being (Hofferth and Hayes, 1987). For example, there is ample evidence to support a link between teenage childbearing and negative outcomes in later life (e.g., Fletcher and Wolfe, 2009; Geronimus and Korenman, 1993). Moreover, sexual activity of adolescents has been found to be associated with symptoms of depression (Sabia and Rees, 2008). Becker’s (1973) seminal work on the theory of marriage (and more generally of the formation of a marital union)

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predicts that individuals who are more physically attractive enjoy greater gains to marriage and hence are more likely to enter a union. Nonmarket traits such as beauty enhance nonmarket productivity (among the commodities produced in the union Becker lists are ‘‘prestige,’’ ‘‘love,’’ ‘‘companionship,’’ and ‘‘recreation’’). While relationships among teenagers differ from marital unions in many important ways (e.g., teenage couples typically do not live together, have children, or stay together for an extended period), Becker’s idea of productivity-enhancing effects of desirable traits such as physical attractiveness, broadly understood, provides one important rationale for hypothesizing a causal relationship between appearance and the likelihood of having relationship experience and engaging in different modes of sexual activity. To the extent that largeness, as proxied by elevated BMI levels, is perceived as unattractive, we may expect that obese adolescent females are less likely to have romantic relationships and sexual experiences, all else equal. Moreover, if the ranges of BMI values considered attractive differ for black and white female adolescents, or if being overweight or obese is stigmatized less among black teenagers compared to whites, then we would expect to observe race-specific effects of body size. We will investigate these hypotheses using unique data on interviewer-based assessments of subjects’ appearance and personality available in our data set. Competing with the ‘‘success through beauty’’ hypothesis, which arises from framing the problem of adolescent dating and sexual activity in the context of relationship markets, are alternative motivations and mechanisms such as the desire to engage in risky behaviors and peer pressure. Teenagers, especially those from socio-economically disadvantaged environments, may engage in risky behavior including sex as an ‘‘alternative expression of self-worth’’ (Petersen et al., 2004). If there are unmeasured individual-level or environmental influences that cause both elevated body weight and a greater interest in dating and sexual activity, then the estimated relationship between body weight and dating and sexual behaviors may be biased. To investigate the role of these factors, we utilize proxies and attitudinal data on sex and risky behaviors and estimate school fixed effects models as well. Adolescents’ dating and sexual experiences may also affect their health and eating behavior. For example, early sexual activity has been found to be predictive of certain symptoms of depression (Sabia and Rees, 2008) which may in turn lead to poor weight outcomes (Mamun et al., 2009). On the other hand, rejection in the dating market may cause eating disorders and affect weight. We examine estimates from models using lagged weight measures and instrumental variables to address these reverse causality concerns. We find that obese white female adolescents are less likely to be in a romantic relationship compared to their non-obese counterparts. In addition, obese white girls are also less likely to have been intimate and to have had sex. Our analysis did not reveal such differences in the relationship experiences and sexual behaviors of obese and non-obese black female adolescents. These findings are novel and contribute to the emerging literatures on the

consequences of obesity and racial differences in appearance norms. 2. Data and methods 2.1. Data source and analysis sample The data for this study are drawn from the National Longitudinal Survey of Adolescent Health (henceforth ‘‘Add Health’’). Add Health surveyed adolescents from 132 schools nationwide between grades 7–12 during the 1994–1995 school year (20,745 respondents), with a follow-up survey in 1996 (about 15,000 respondents). In addition, one parent (mostly mothers) for each adolescent was interviewed as part of the in-home parent survey during the first wave in 1994–1995. The final samples in this study are drawn primarily from wave II (1996) female respondents in grades 7 through 12 under the age of 19. For each individual, we link the data with the parent survey in 1994–1995, yielding a sample of 4027 non-Hispanic white females and 1739 non-Hispanic black females used in our analysis. 2.2. Measures 2.2.1. Outcome variables Our outcome variables consist of the following 3 selfreported measures of dating and sexual experiences: (i) being involved in a romantic relationship in the last 18 months (outcome variable ‘‘Was in Romantic Relationship’’); (ii) ever being touched in the genital area in a sexual way (outcome variable ‘‘Was touched in Genital Area’’); (iii) ever engaging in sexual intercourse (outcome variable ‘‘Had Sex’’). 2.2.2. Explanatory variables The main explanatory variables of interest are BMI zscore7 and whether the person is obese. These measures were calculated using the Centers for Disease Control and Prevention (CDC) growth charts for 2000 and are based on the adolescent’s BMI [weight(kg)/height(m2)] relative to the national distribution and are age- and gender-specific. Adolescents who are at the 95th percentile or above are classified as being obese.8 Wave II of Add Health contains interviewer-measured height and weight of the adolescents and thus our measure of body weight is not subject to self-reporting bias. Our control variables include basic demographic characteristics such as age, grade level, whether first-born, religion and whether the subject has any siblings. The parent survey of Add Health allows us to control for a number of parental and family characteristics including mother’s education, father’s education, age when the respondent moved to her current place of residence,

7 BMI z-score indicates how many standard deviations apart an adolescent’s BMI is from the mean BMI of the population reference group for their age and sex. 8 We focus on this weight category because the relationship penalty borne by obese adolescents is greater compared to other weight categories.

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whether the family is currently receiving welfare benefits and whether the neighborhood was chosen because of the school district. Other control variables include measures of the individual’s physical attractiveness as reported by the interviewer on a five point Likert scale. Add Health required the interviewers to describe the respondent as soon as possible after leaving the individual’s home. In a unique set of questions, the interviewer was asked to grade the physical attractiveness and the personality of the respondent, providing us with more objective assessments of physical appearance and personality. Responses ranged from ‘‘very unattractive,’’ ‘‘unattractive,’’ ‘‘about average,’’ ‘‘attractive’’ to ‘‘very attractive’’ with 1 being ‘‘very unattractive’’ and 5 being ‘‘very attractive’’. The interviewer was also asked to comment on how well groomed and candid the respondent was on a similar scale. In addition, the interviewer was asked how physically mature was the respondent compared with other adolescents of her age with 1 being ‘‘very immature’’ to 5 being ‘‘very mature.’’ In addition to the control variables we account for variables that could potentially mediate the relationship between body size and dating/sexual behaviors. These mediator variables include motivation to engage in sexual intercourse and substance abuse such as getting drunk in the past 12 months and using drugs in the last 30 days. Consumption of alcohol and drugs has been frequently linked to sexual behaviors (e.g., Grossman and Markowitz, 2005). We utilize data on drug and alcohol use also in an attempt to proxy for otherwise unobserved heterogeneity in attitudes toward risky behaviors. Further, we employ two direct measures of motivations for sexual intercourse. The first variable indicates whether the adolescent feels that their friends would respect them more if they had intercourse and the second variable indicates whether the adolescent feels that having intercourse would make them more attractive to the opposite sex. Other mediators that we utilize are measures of whether the individual has exercised at least three or more times during the past seven days; whether the individual plays an active sport such as baseball, softball, soccer, swimming or football; the individual’s self reported health status; and two measures of mental health. The first mental health measure is an abridged Rosenberg SelfEsteem (RSE) Scale (Rosenberg, 1965) and the second measure is based on the Center for Epidemiologic Studies Depression (CES-D) Scale (Radloff, 1977), a widely used measure of depressive symptoms.9 These measures of physical and mental health may capture important differences in individual characteristics such as levels of self-esteem and personality type. 2.3. Sample descriptive statistics Summary statistics on adolescent dating experience and sexual behavior (outcome variables), measures of

9 For details on how these abridged mental health indicators were constructed using Add Health please see Ali et al. (2011b) and Sabia and Rees (2008).

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body weight, interviewer-provided assessment of attractiveness, and variables used to instrument the body size measures are reported in Table 1. Similarly, Appendix Table A1 reports sample statistics for the other control variables.10 The mean BMI z-score among the non-Hispanic white female adolescents is 0.25, compared to 0.51 for nonHispanic blacks, indicating that white females on average have a lower body weight compared to black females. The corresponding obesity rates are 9.5% for whites and 15.8% for blacks. From the table we can see that white females are more likely to have had a romantic relationship in the last 18 months than black females (62.6% white vs. 52.4% black). Table 1 also shows that the white girls in our sample are less likely to have had sex (intercourse) than black girls (40.5% white vs. 50.2% black). White girls are also slightly less likely to have experienced touching in the genital area in a sexual way (55.6% white vs. 57.4% black). 2.4. Multivariate analysis We estimate linear regression models (OLS) of adolescent romantic relationships and sexual behaviors. In our most comprehensive model, the propensity to participate in such activities by individual i in school s, interviewed by interviewer k, at time t, is given by Y iskt ¼ a þ b1 W iskt þ b2 X ist þ b3 Piskt1 þ b4 Hiskt þ b5 Aiskt þ g s þ dk þ eiskt

(1)

where Y iskt and W iskt refer to the adolescent experience and participation in sexual activities and weight status (BMI zscore or a binary indicator of being obese) respectively, measured in 1996 (i.e., t = 1996). The vector of individual demographic characteristics measured in 1996 and family characteristics measured from the parent survey in 1994 is denoted by X iskt and P iskt1 , respectively. The vector Hiskt captures the adolescents’ health status such as self-rated good health, mental health indicators (the CES-D and RSE scale), whether the adolescent exercises regularly, and whether the adolescent plays an active sport and indicators for substance abuse. The vector Aiskt denotes

10 Out of a total of 5766 (1739 black and 4027 white) non-Hispanic females, 2162 (616 black and 1546 white) females had missing values for ‘‘Respect as a motivation to engage in sex’’, 2184 females (623 black and 1561 white) had missing values for ‘‘Being attractive as a motivation to engage in sex’’, 14 (8 black and 6 white) females had missing values for ‘‘RSE-score’’, 85 (16 black and 69 white) females had missing values on variable ‘‘Drugs’’, 447 (148 black and 299 white) females had missing values for ‘‘Age at first period’’, and 676 (190 black and 486 white) females had missing information on grade level. In order to minimize the sample loss, we have imputed the missing values on these explanatory variables with either a sample mean or the most frequent category (if binary). In all of our regression results, we have included a set of dummy variables indicating missing values for each of these explanatory variables. Our final analysis sample consisted of 5766 observations (1739 black and 4027 white females). In order to evaluate the impact of sample restriction, we have tabulated percent differences between the averages of the analysis sample and the original sample with the associated p-values from a t-test of the difference in the averages (columns 4 and 7 of Table 1 and Appendix Table A1). With the exception of the variables measuring motivations to engage in sex and maternal disapproval of sex, all other differences are not statistically significant.

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Table 1 Descriptive statistics for outcome measures, body size measures, instrumental variable, and interviewer assessments. Hon-Hispanic black females Mean

St. dev.

Outcome measures Romantic relationship in the last 18 months Ever been touched in genital area in sexual way Ever had sex (intercourse)

0.532 0.582 0.52

0.499 0.493 0.5

Body weight measures BMI z-score Obese BMI z-score (1994) Obese (1994)

0.522 0.16 0.562 0.129

1.088 0.367 0.968 0.335

Instrument Mother obese

0.143

0.35

3.58 3.642 3.542 1.745 3.546

0.811 0.836 0.789 0.868 0.852

Interviewer rated attractiveness Physically attractive Attractive personality Well groomed Candid Physically mature Observations

1739

Non-Hispanic white females % diff.

Mean

St. dev.

% diff.

0 0 0

0.639 0.58 0.42

0.48 0.494 0.494

0 0 0

0 0 0 0

0.232 0.093 0.222 0.069

1.041 0.291 0.967 0.253

1 1 1 0

1

0.161

0.367

0

0 0 0 0 0

3.716 3.706 3.571 1.515 3.473

0.821 0.805 0.774 0.725 0.794

0 0 0 0 0

4027

* Significance level p < 0.10. ** Significance level p < 0.05. *** Significance level p < 0.01. Note: The column ‘‘% diff.’’ refers to percentage difference between the averages of a variable in the analysis sample (Mean) and in the original Add Health data. The corresponding statistical significance levels for the t-test of equality of the means are indicated. See the text for the information about construction of the analysis sample.

the attractiveness of the adolescent as rated by the Add Health interviewer (k), g s is a vector of school dummy variables that control for unobserved school type (schoollevel fixed effects) or environmental confounders, dk is a vector of interviewer dummy variables that control for unobserved interviewer characteristics (interviewer fixed effects), and eiskt is the error term. We seek to measure the role of weight status on individuals’ sexual and dating experiences and behaviors, b1. We begin by estimating relatively parsimonious models and then consider models with an increasingly large set of controls to assess the robustness of the estimated effects and examine hypothesis regarding factors that may mediate the relationship of interest. Our most comprehensive model is shown in Eq. (1). Conventional estimates of Eq. (1) may be subject to bias from two sources. First, common unobserved environmental factors may lead to a correlation between weight status and sexual behaviors. These environmental factors may lower the opportunity cost of dating and engaging in (risky) sexual behaviors. For example, adolescents who grow up in environments of concentrated economic disadvantage and social disorganization may seek ‘‘alternative expression of self-worth’’ manifesting as risky behavior including sex, drug or violence (Petersen et al., 2004). Unobserved environmental characteristics could also include confounding factors such as proximity to fast-food restaurants, the availability of vending machines, opportunities to expend energy (e.g., exercise facilities), the percentage of the population in poverty, and the proportion of adolescents engaging in sexual behaviors. These factors

are correlated with both Y iskt and W iskt and when unmeasured, can lead us to incorrectly attribute causal effects in individuals’ sexual behaviors when none might exist. Second, it is possible that the estimated effects of body size suffer from reverse causality or simultaneity bias. There is evidence that sexual activities are associated with symptoms of depression (Sabia and Rees, 2008), which in turn could lead to poor weight outcomes (Mamun et al., 2009). Reverse causality is especially a concern here since we relate body size measured in 1996 to outcomes of processes that started earlier. If either or both of these problems are present, a fundamental assumption for consistency of the estimation to give b1 a causal interpretation will be violated. In this case, the error term, e, will be correlated with both Y and W so that E(ejW) 6¼ 0. One important feature of the Add Health data is that it allows us to control for environmental confounders at the school level using a vector of school dummy variables, g s . These school fixed effects will account for any common environmental characteristics at the school level that may be correlated with both body weight and sexual behaviors. We are interested in controlling for such effects since it is likely that schools differ in the socioeconomic and demographic composition of their student body as well as in community-level characteristics or institutional features that are correlated with our outcomes of interest. For example, an adolescent who attends a school where poverty rates and violent crime are high, fast-food chains abound, or public recreational facilities are scarce may be more likely to be sexually active and also have higher body weight.

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To address potential biases due to reverse causality or simultaneity, we rely on two additional estimation strategies. First, owing to the longitudinal nature of our data, we can use lagged values of body weight.11 Replacing Wiskt with Wiskt  1 we may obtain better estimates of the effect of body size since adolescents’ sexual behaviors in period t (1996) is correlated with their body weight in the previous period t  1 (1994), but their sexual behavior in period t cannot influence their body weight status in period t  1. To express this more formally, we can amend our standard model in Eq. (1) and estimate the following model: Y iskt ¼ a þ b1 W iskt1 þ b2 X iskt þ b3 P iskt1 þ b4 Hiskt þ b5 Aiskt þ g s þ dk þ eiskt

(2)

We note that Eq. (2) results in the estimation of a different effect (that of lagged body size) which may not yield satisfactory results if the inter-temporal correlation of weight status is weak (raising the problem of the length of the optimal lag). However, given the longitudinal nature of the process governing our dependent variable, which may reflect weight outcomes that have occurred much earlier, the respondents’ body size in the past may in fact be the more relevant predictor than contemporaneous body size. We also pursue a second alternative strategy, utilizing an instrumental variables approach (2SLS). The instrumental variable estimator (IV) provides a consistent estimator under the assumption that the instruments (Z) are variables that are correlated with the regressor, W, that satisfy E(ejZ) = 0 (Newhouse and McClellan, 1998). It is possible to obtain the instrumental variable estimator through the linear instrumental variable model, which is a two-stage model that first deals with predicting the weight status variable we want (stage 1) and using the predicted value of the weight variable into the sexual behavior regression (stage 2).12 The first stage thus estimates the following equation W iskt ¼ h þ a1 Z iskt þ b2 X iskt þ b3 Piskt1 þ b4 Hiskt þ b5 Aiskt þ g s þ dk þ miskt

(3)

Proper implementation of the IV requires having access to instruments (Z) that satisfy two properties. First, they influence (cause variation in) the variable whose effect we want to understand; in our case the

11 The lagged body weight measures were obtained from self-reported height and weight since measured height and weight were not available in wave I of Add Health. 12 Using probit regression and probit IV regression produced similar results to those reported below. In this paper we only report results from linear regression models, which are more robust to the inclusion of a large number of fixed effects (interviewer- and school-specific effects in our case) than is the non-linear probit model. Neyman and Scott (1948) demonstrate that the fixed effects maximum likelihood estimator of the probit model may result in inconsistent estimates on all parameters due to the ‘‘incidental parameters problem’’. Also, our preferred approach is consistent with Sabia and Rees (2011b) and Averett et al. (2013) who also use linear regression estimation to study the effects of body weight on adolescent sexual behavior. The probit model results are available from the authors upon request.

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weight measure. Second, these instruments (Z) must have no direct effect on the outcome measure (Yiskt in Eq. (1)) so they must be independent of the latent factors that drive that outcome. In other words, as long as Z is legitimately excludable from Eq. (1), this method can identify a causal relationship from weight status to sexual behaviors. For our instrument we follow previous work (Ali et al., 2012; Renna et al., 2008; Trogdon et al., 2008) and consider the obesity status of the biological mother, as a candidate for instrument.13 We require that this variable directly impact the individual’s weight status but do not directly predict individual sexual and dating activities. In particular, we assume that, while individuals who have an obese mother are more likely to be obese themselves, the obesity status of the mother will only directly affect their weight status but not their sexual behaviors. This condition is violated if there are characteristics of the mother (or other factors affecting her weight status) that also directly influence the dating behavior and sexual experiences of the adolescent. This would be the case, for example, if low self-esteem and preferences for risk-taking were unobserved and intergenerationally shared determinants of dating/sex and weight. We include measures of low self esteem and risk preferences and an array of other controls in our models that would potentially control for these and other possible sources of endogeneity. In addition, we perform several robustness checks on our instrument. As shown below, we also provide statistical evidence that our instruments are valid. Thus, similar effects found across our main strategies to deal with potential endogeneity, the school-level fixed effects models, the lagged weight status models as well as the IV models, would provide evidence suggestive of a causal interpretation of the relationship between body size outcomes and sexual and dating experiences and behaviors. 3. Main results Table 2 present the estimates of the effect of being obese and BMI z-score on dating experience and sexual behaviors for female adolescents from our model under alternative specifications. To conserve space, we only present and discuss estimates on the main variables of interest – being obese and BMI z-score. The estimated effects of the other explanatory variables from the various specifications are available from the authors upon request. The baseline model includes two measures of personality (attractive personality, candid), three measures of physical appearance (physically attractive, well groomed, physically mature) as reported by the interviewer along with school-level fixed effects, and interviewer fixed effects. The baseline model also includes age, grade level, whether first born, whether the respondent has siblings, mother’s education, father’s education, whether family is on welfare, indicator for religion, age when moved to the

13 Previous literature has discussed the appropriateness of using a biological relative’s weight as an instrument (Cawley, 2004; Lindeboom et al., 2010).

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Table 2 OLS estimates of the effect of obesity/BMI on dating and sex, by race. Non-Hispanic white females Baseline model

Non-Hispanic black females

Model with mediators

Lagged model

Baseline model

Model with mediators

Lagged model

Was in romantic relationship Obese 0.159*** (0.029) Observations 4027 0.236 R-squared BMI z-score 0.046*** (0.009) Observations 4027 R-squared 0.236

0.158*** (0.030) 4027 0.275 0.050*** (0.009) 4027 0.276

0.130*** (0.031) 4027 0.271 0.057*** (0.009) 4027 0.277

0.016 (0.048) 1739 0.260 0.001 (0.016) 1739 0.260

0.029 (0.045) 1739 0.287 0.006 (0.015) 1739 0.287

0.032 (0.037) 1739 0.287 0.011 (0.016) 1739 0.287

Was touched in genital area Obese 0.117*** (0.029) Observations 4027 R-squared 0.282 BMI z-score 0.009 (0.008) Observations 4027 R-squared 0.278

0.121*** (0.026) 4027 0.362 0.015* (0.008) 4027 0.358

0.129*** (0.025) 4027 0.361 0.015* (0.008) 4027 0.358

0.018 (0.039) 1739 0.251 0.006 (0.013) 1739 0.251

0.034 (0.035) 1739 0.288 0.013 (0.013) 1739 0.288

0.024 (0.038) 1739 0.287 0.007 (0.015) 1739 0.287

0.112*** (0.022) 4027 0.420 0.028*** (0.007) 4027 0.419

0.138*** (0.027) 4027 0.420 0.033*** (0.007) 4027 0.419

0.004 (0.041) 1739 0.315 0.011 (0.015) 1739 0.316

0.028 (0.037) 1739 0.368 0.002 (0.015) 1739 0.368

0.084* (0.047) 1739 0.371 0.001 (0.018) 1739 0.368

Had sex Obese Observations R-squared BMI z-score Observations R-squared

0.116*** (0.024) 4027 0.347 0.024*** (0.008) 4027 0.345

Note: Estimates from a linear (OLS) model. Standard errors corrected for clustering at the school level are reported in parentheses. The covariates in the baseline model include school level and interviewer fixed effects in addition to the following controls: age, grade level, first born, whether has siblings, mother’s educational categories, father’s educational categories, family on welfare, and parent chose current location because of school district, measures of personality (attractive personality, candid) and three measures of physical appearance (physically attractive, well groomed, physically mature) as reported by the interviewer, religion dummies,. The model with mediators additionally included the following variables: whether adolescent believes having sex will make her more attractive to the opposite sex, whether believes friends will respect her more if she has sex, age at first period, indicators of self-rated health, whether exercises regularly, whether participates in an active sport, two indicators of mental health (CES-D score and RSE score), and whether the adolescent consumed alcohol in the past month or used illegal drugs in the past month. Lagged model includes all covariates from the model with mediators, but uses lagged (1994) measures of body weight. * Significance level p < 0.10. ** Significance level p < 0.05. *** Significance level p < 0.01.

current location and whether parent chose current location because of school district.14 We then modify the baseline model to include the following mediators: whether the adolescent believes having sex will make her more attractive to the opposite sex, whether she believes friends will respect her more if she has sex, age at first period (menarche), indicators of self-rated health, whether she exercises regularly, whether she participates in an active sport, two indicators of mental health (CES-D score and RSE score), whether the adolescent got drunk in the past 12 months

14 The variables ‘‘parent chose current location because of school district’’ and ‘‘age when moved in the current location’’ were included in order to address sorting into different schools based on family traits. None of these variables was significant, indicating no support for sorting into different schools.

and whether she used illegal drugs in the past month, Finally, the lagged model includes all of these variables but the body weight measures are lagged (obtained from wave I of the data). Observing the results for white females in Table 2 from the baseline model, we find that higher body weight and being obese are associated with a lower likelihood of being in a romantic relationship in the last 18 months. Specifically, the results show that white obese women have approximately 16% lower probability of having a romantic relationship in the past 18 months and that a one standard deviation increase in BMI would reduce the probability of having a relationship experience by 0.047 percentage points. Investigating how the estimated effects of obesity and BMI z-score on relationship experience changes from the baseline specification when only school and interviewer fixed effects, as potential mediators are added we find that

M.M. Ali et al. / Economics and Human Biology 12 (2014) 140–152

the magnitude of the effect of being obese and BMI z-score are quite robust. It is interesting to note that variables such as religious background and attitudes toward sex, physical and mental health as well as consumption of alcohol and drugs, and interviewer-assessed personality and attractiveness do not modify the relationship between body size and the likelihood of having been in a romantic relationship by much. While these variables are likely to only imperfectly proxy for the preferences, risk-appetite, self-esteem, and personality of a person, taken at face value the results reject the notion that differences in attitudes, tastes for risk, or low self-esteem between obese and non-obese white female adolescents can explain the relationship between body size and dating. Furthermore, accounting for common unmeasured factors at the school level using school fixed effects does not alter the relationship in a significant way either. Table 2 also shows the estimated relationship between body size and sexual experiences. The results show that white female adolescents that are obese or have a higher BMI are less likely to have had sex (intercourse) or to have been touched in the genital area in a sexual way. Unlike the dating experience outcome, the link between body size and likelihood of being touched in the genital area appears to be mediated to some extent by our set of included covariates, as indicated by a decreased coefficient on obesity. This is also the case for the outcome of having had sex. Table 2 reports the estimated coefficients for BMI zscore and obesity in the dating and sexual behavior for black female adolescents. As shown in the table, the estimates suggest that BMI and obesity have no systematic relationship with whether the person was in a romantic relationship during the past 18 months. Consistent with the findings on dating experience, we find no evidence that physical appearance as captured by measures of body size is related to sexual behaviors. Table 2 also presents estimates using lagged measures of BMI and obesity instead of the contemporaneous ones used previously (weight status measured in 1994 survey rather than 1996). As explained in Section 2.4 there are several reasons for considering this specification. As the table shows, the results follow a similar pattern as those above but the estimated magnitudes tend to be smaller. Obese white adolescent females are 13% less likely to have been in a romantic relationship in the last 18 months, 14% less likely to ever have had sex, and 13% less likely to ever have been touched in the genital area in a sexual way. The regressions using BMI z-score suggest a negative link between body size and the likelihood of being in a romantic relationship and the likelihood of ever having had sex. The estimated magnitudes of these relationships are roughly consistent with the contemporaneous estimates. The smaller magnitude of the coefficients when using the obesity indicator but not when using BMI z-score are consistent with the idea that the estimates using obesity status in 1996 overstate the true effects of large body size due to a feedback loop between relationship outcomes and weight. For example, disappointment over the lack of prospects in the dating market may manifest

147

itself in poorer eating and exercise habits and ultimately lead to abnormal weight gain. Table 3 presents instrumental variable estimates of the effect of BMI z-score and obesity in the baseline model (Appendix Tables A2A and A2B report estimates on all of the explanatory variables in the models for obesity).15 The point estimates of the effects tend to be greater with larger standard errors. However, the overall pattern is consistent with the results from the single equation estimates. White female adolescents who are obese (have a higher body weight) are less likely to be in a romantic relationship compared to their non-obese (lower body weight) counterparts. In addition, the results suggest that obese (high body weight) white girls are less likely to ever have been intimate (touched in genital area) or to have had sexual intercourse. Further, as in our estimates from single equation models, the IV estimates suggest that body size is unrelated to dating and sexual experiences of black girls.16 Our first stage F-statistics, the first-stage p-value and the coefficient of mother’s obesity in the first stage also provide evidence to support its validity as a variable excludable from the outcome equation. While these test statistics should not be taken as conclusive evidence of the exogeneity of the instrument, it seems unlikely that there is any direct influence of mothers’ weight status on individual’s sexual and dating behaviors. Therefore, it is reasonable to argue that our instrument satisfies the exclusion restriction.17 We also performed another test of our findings – by reestimating our models for non-Hispanic white and black males. Burke and Heiland (2008) showed that ideal weight for black and white males are very similar, which leads one not to expect a significant race difference in the effect of body weight on sexual and romantic relationships for males. Our results confirm this expectation and are available upon request.18 4. Discussion and conclusion Using large, representative samples of white and black female adolescents from Add Health, we find evidence that obese white female adolescents are significantly less likely to have been in a romantic relationship compared to their non-obese counterparts. In addition, obese white girls are

15 It is important to note that estimating instrumental variable models with the mediator variables included does not substantially change the results. 16 We have also estimated all models for the overweight indicator (>85th BMI percentile) and obtained results that were qualitatively similar to the results on obesity indicator. The magnitudes of the coefficients on the overweight indicator, however, were smaller than those on the obesity indicator. The results with overweight indicator are available upon request. 17 As an additional robustness check of the exclusion restriction of our instrument, we included maternal obesity in the second stage of the instrumental variable regression. This test strongly supported the excludability of the instrument. 18 Following suggestion from an anonymous referee, we also estimated sibling fixed effects models. However, low numbers of siblings available in Add Health did not allow us to obtain estimates of the effects of obesity and BMI by race at conventional levels of statistical significance.

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M.M. Ali et al. / Economics and Human Biology 12 (2014) 140–152

Table 3 Instrumental variable estimates of the effect of obesity/BMI on dating and sex using the baseline model, by race.

Non-Hispanic white females Obese Observations First-stage F-statistic First-stage p-value First-stage coefficient on IV BMI z-score Observations First-stage F-statistic First-stage p-value First-stage coefficient on IV Non-Hispanic black females Obese Observations First-stage F-statistic First-stage p-value First-stage coefficient on IV BMI z-score Observations First-stage F-statistic First-stage p-value First-stage coefficient on IV

Was in romantic relationship

Was touched in genital area

Had sex

0.501*** (0.186) 4027 51.865 0.000 0.118***

0.397** (0.177) 4027 51.865 0.000 0.118***

0.413** (0.166) 4027 51.865 0.000 0.118***

0.132*** (0.047) 4027 96.110 0.000 0.449***

0.104** (0.046) 4027 96.110 0.000 0.449***

0.109** (0.043) 4027 96.110 0.000 0.449***

0.008 (0.277) 1739 14.288 0.000 0.123***

0.086 (0.278) 1739 14.288 0.000 0.123***

0.561* (0.298) 1739 14.288 0.000 0.123***

0.003 (0.087) 1739 24.494 0.000 0.392***

0.027 (0.087) 1739 24.494 0.000 0.392***

0.176* (0.089) 1739 24.494 0.000 0.392***

Note: Estimates are from a linear instrumental variable (2SLS) model. The instrument is the mother’s obesity indicator. Standard errors corrected for clustering at the school level are reported in parentheses. ‘‘First stage F-statistic’’ and ‘‘First-stage p-value’’ refer to the F-test of the coefficient on the instrument (mother’s obesity indicator) in the first-stage regression. For the list of other covariates included in each model, see note to Table 2 about the baseline model. * Significance level p < 0.10. ** Significance level p < 0.05. *** Significance level p < 0.01.

significantly less likely to have been physically intimate and to ever have had sex. We find no statistically significant differences in relationship experiences and sexual behaviors between obese and non-obese black female adolescents. Overall, the estimates are quite robust to alternative specifications and we are able to confirm the patterns with instrumental variables estimates and estimates from models using lagged weight status. The finding that body weights are predictive of relationship experience for white female adolescents is consistent with related work using pooled (by race/ ethnicity) samples (Averett et al., 2013; Cawley et al., 2006; Sabia and Rees, 2011b) and evidence from U.S. adult relationship markets that (white) men value thinness, on average, such that obese women are less likely to be in a cohabiting or marital union (Averett and Korenman, 1996, 1999; Mukhopadhyay, 2008). Empirically confirming the existence of an adolescent relationship premium for being thin and a punishment for being obese is broadly consistent with the economic theory of marital union formation (Becker, 1973), which predicts that desirable non-market traits enhance nonmarket productivity and make individuals possessing these traits more likely to enter a relationship. The

presence of social norm of thinness as a desirable appearance attribute among white and not necessarily among black females implies that the thinness premium (or obesity penalty) in the dating and sexual relationship markets that we found among white girls but not among black girls is consistent with this economic explanation. However, it is important to note that delayed sexual initiation has been shown to be correlated with better educational outcome among female adolescents (Sabia and Rees, 2011a,b). As such, it is plausible that an overweight female with delayed sexual initiation might have better educational outcomes and consequently experience better economic condition and stability as they transition into adulthood. This is an interesting direction for further research. Given that the interviewers (raters of physical attractiveness) in our sample are all adult females, their perceptions of female adolescent’s physical attractiveness and maturity is likely to be a noisy proxy of (primarily) male adolescents that comprise the set of potential partners (see Ali et al., 2013 for a detailed discussion). Future research into this mechanism using assessments by peers is needed. If the pattern can be confirmed, it would lend support to the hypothesis, derived from

M.M. Ali et al. / Economics and Human Biology 12 (2014) 140–152

Becker’s theory of union formation as discussed in Section 1, that body size is an important attribute in the relationship market of white female adolescents complementing other priced characteristics like fitness and health and broader measures of physical attractiveness and maturity. Our main findings that the relationship between a large body size and the likelihood of having been in a relationship and having sexual experiences differs by race is consistent with race-specific differences in how the dating partners (primarily the male peers) value female largeness by race. One hypothesis that can be examined in future research is that the physical attractiveness of black girls is less related to body size than the attractiveness of white girls. In addition to the evidence obtained here, an increasingly rich body of evidence exists to support the view that cultural differences in ideal body size, obesity stigma, and related identity prescriptions may contribute to racial differences in the effect of body size on adolescents’ dating and sexual experiences and behaviors. Researchers have hypothesized that departure of selfassessments from objective standards indicates that sociocultural influences, and social weight comparisons in particular, play an important role in such assessments (see e.g., Burke and Heiland, 2007; Trogdon et al., 2008).19 Black women have been found to be less likely than women in other racial/ethnic groups to perceive themselves as overweight, even after controlling for objective weight status (see Molloy and Herzberger, 1998). Dale and Thompson’s (1997) analysis of the body sizes of photographic images in women’s magazines found that Essence, a magazine targeting a primarily black audience, had the largest average image size (‘‘body shape rating’’).

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Using self-perception data from a nationally representative sample of women age 25–74, Burke and Heiland (2008) estimate that the ideal BMI is roughly three points greater for blacknon-Hispanicwomencomparedtowhitenon-Hispanic women. Other studies comparing actual and perceived weight status also suggest that misperception of overweight status is more prevalent among African-Americans women (Paeratakul et al., 2002). Moreover, stigmatization of obesity in others – which may vary independently of ideal weight – has been shown to be weaker among black men compared with white men and women. Our findings are thus consistent with race-specific differences in penalties associated with obesity found in related research. Acknowledgement The views expressed in this paper are those of the authors and do not necessarily represent the views of the Substance Abuse & Mental Health Services Administration. This research uses data from Add Health, a program project directed by Kathleen Mullan Harris and designed by J. Richard Udry, Peter S. Bearman, and Kathleen Mullan Harris at the University of North Carolina at Chapel Hill, and funded by grant P01-HD31921 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, with cooperative funding from 23 other federal agencies and foundations. Special acknowledgment is due Ronald R. Rindfuss and Barbara Entwisle for assistance in the original design. Information on how to obtain the Add Health data files is available on the Add Health website (http:// www.cpc.unc.edu/addhealth). No direct support was received from grant P01-HD31921 for this analysis. Appendix A

Table A1 Descriptive statistics for other covariates. Hon-Hispanic black females

Demographics Age Grade level Seven Eight Nine Ten Eleven Twelve Grade level missing Religion Catholic Protestant Other religion No religion First born Has siblings Motivations to engage in sex Respect

Mean

St. dev.

16.126

1.649

0.015 0.145 0.166 0.177 0.196 0.193 0.109

Non-Hispanic white females Mean

St. dev.

0

15.995

1.621

0

0.121 0.353 0.372 0.381 0.397 0.394 0.312

0 0 0 0 1 0 0

0.01 0.17 0.161 0.195 0.185 0.158 0.121

0.102 0.376 0.368 0.396 0.388 0.364 0.326

4 0 0 1 0 0 0

0.041 0.826 0.036 0.097 0.531 0.731

0.199 0.379 0.185 0.296 0.499 0.443

0 0 5 0 0 0

0.221 0.566 0.052 0.161 0.502 0.814

0.415 0.496 0.222 0.368 0.5 0.39

0 0 0 1 1 0

0.055

0.227

56***

0.022

0.145

63***

19 A number of recent papers find evidence in cross-sectional data that supports this hypothesis (Ali et al., 2011a; Maximova et al., 2008).

% diff.

% diff.

M.M. Ali et al. / Economics and Human Biology 12 (2014) 140–152

150 Table A1 (Continued )

Hon-Hispanic black females

Respect (missing) Attractive Attractive (missing) Health measures Self-reported good health RSE score RSE score (missing) CES-D score Exercises regularly Plays an active sport Drunk Drugs Drugs (missing) Age at first period Age at first period (missing) Parental characteristics Mother college Father college Mother some college Father some college Mother high school Father high school Mother less than high school Father less than high school Welfare Chose area because of school district Observations

Non-Hispanic white females

St. dev.

% diff.

0.354 0.04 0.358

0.478 0.195 0.48

0 55*** 0

0.909 25.558 0.005 16.583 0.521 0.502 0.144 0.105 0.009 12.058 0.085

0.287 3.579 0.068 5.639 0.5 0.5 0.352 0.307 0.096 1.344 0.279

0.022 0.028 0.905 0.881 0.033 0.055 0.04 0.037 0.357 0.276

0.148 0.164 0.294 0.324 0.18 0.227 0.195 0.188 0.479 0.447

Mean

Mean

St. dev.

% diff.

0.384 0.032 0.387

0.486 0.175 0.487

0 63*** 0

0 0 0 0 0 0 0 0 0 0 0

0.938 24.553 0.001 15.647 0.525 0.662 0.349 0.16 0.017 12.226 0.074

0.241 3.662 0.039 5.046 0.499 0.473 0.477 0.367 0.13 1.222 0.262

0 0 0 0 0 0 0 2 0 0 0

2 0 0 0 1 2 3 0 0 0

0.017 0.043 0.941 0.855 0.025 0.065 0.016 0.037 0.189 0.471

0.131 0.203 0.235 0.352 0.156 0.247 0.127 0.189 0.392 0.499

36 12 1 1 5 0 5 0 1 0

1739

4027

Note: see note to Table 1. *** Significance level p < 0.01.

Table A2A Full set of instrumental variable estimates of the effect of obesity on dating and sex using the basline model, by race. First stage results.

Mother obese Age First born Has siblings Grade seven Grade eight Grade nine Grade ten Grade eleven Grade twelve Mother college Father college Mother some college Father no high sch. Mother no high sch.

Table A2A (Continued )

Non-Hispanic white females

Non-Hispanic black females

Father some college

0.118*** (0.016) 0.001 (0.007) 0.016 (0.010) 0.014 (0.014) 0.030 (0.065) 0.009 (0.037) 0.004 (0.030) 0.007 (0.021) 0.009 (0.016) 0.006* (0.004) 0.032 (0.045) 0.001 (0.029) 0.018 (0.031) 0.021 (0.033) 0.018 (0.058)

0.123*** (0.033) 0.014 (0.012) 0.015 (0.024) 0.003 (0.027) 0.126 (0.104) 0.055 (0.060) 0.013 (0.049) 0.034 (0.038) 0.026 (0.030) 0.008 (0.007) 0.046 (0.078) 0.023 (0.067) 0.046 (0.048) 0.013 (0.066) 0.170** (0.072)

On welfare Chose school Catholic Other religion No religion Attractive Personality Candid Physically attractive Well groomed Physically mature

School fixed effects Interviewer fixed effects Observations R-squared Note: see note to Table 3. * Significance level p < 0.10. ** Significance level p < 0.05. *** Significance level p < 0.01.

Non-Hispanic white females

Non-Hispanic black females

0.010 (0.020) 0.004 (0.014) 0.017* (0.010) 0.028** (0.012) 0.000 (0.021) 0.032** (0.014) 0.031*** (0.008) 0.004 (0.009) 0.106*** (0.009) 0.021** (0.009) 0.029*** (0.008)

0.025 (0.042) 0.023 (0.022) 0.014 (0.023) 0.089* (0.050) 0.106** (0.044) 0.033 (0.038) 0.027* (0.016) 0.006 (0.017) 0.131*** (0.017) 0.032* (0.017) 0.041*** (0.014)

Included Included 4027 0.227

Included Included 1739 0.258

M.M. Ali et al. / Economics and Human Biology 12 (2014) 140–152

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Table A2B Full set of instrumental variable estimates of the effect of obesity on dating and sex using the baseline model, by race. Second stage results. Non-Hispanic white females

Obese Age First born Has siblings Grade seven Grade eight Grade nine Grade ten Grade eleven Grade twelve Mother college Father college Mother some college Father no high sch. Mother no high sch. Father some college On welfare Chose school Catholic Other religion No religion Attractive personality Candid Physically attractive Well groomed Physically mature

School fixed effects Interviewer fixed effects Observations First-stage F-statistic First-stage p-value Note: see note to Table 3. * Significance level p < 0.10. ** Significance level p < 0.05. *** Significance level p < 0.01.

Non-Hispanic black females

Was in romantic relationship

Was touched in genital area

Had sex

In romantic relationship

Was touched in genital area

Had sex

0.501*** (0.186) 0.023** (0.010) 0.003 (0.017) 0.070*** (0.021) 0.218** (0.104) 0.265*** (0.053) 0.183*** (0.046) 0.132*** (0.033) 0.098*** (0.027) 0.063** (0.025) 0.029 (0.070) 0.001 (0.048) 0.011 (0.047) 0.010 (0.046) 0.096 (0.071) 0.021 (0.032) 0.004 (0.020) 0.013 (0.016) 0.026 (0.021) 0.033 (0.037) 0.035 (0.023) 0.032** (0.014) 0.053*** (0.015) 0.019 (0.024) 0.004 (0.014) 0.047*** (0.013)

0.397** (0.177) 0.044*** (0.011) 0.030* (0.017) 0.088*** (0.022) 0.149 (0.100) 0.286*** (0.054) 0.152*** (0.046) 0.114*** (0.035) 0.087*** (0.029) 0.114*** (0.027) 0.006 (0.070) 0.054 (0.047) 0.009 (0.048) 0.017 (0.048) 0.026 (0.077) 0.044 (0.032) 0.029 (0.020) 0.009 (0.016) 0.006 (0.021) 0.052 (0.036) 0.066*** (0.022) 0.047*** (0.014) 0.027* (0.016) 0.044* (0.023) 0.044*** (0.013) 0.051*** (0.013)

0.413** (0.166) 0.062*** (0.010) 0.024 (0.016) 0.103*** (0.021) 0.230*** (0.084) 0.297*** (0.048) 0.249*** (0.041) 0.207*** (0.033) 0.156*** (0.028) 0.128*** (0.027) 0.094 (0.068) 0.079* (0.046) 0.007 (0.047) 0.082* (0.048) 0.078 (0.076) 0.026 (0.031) 0.059*** (0.019) 0.013 (0.015) 0.016 (0.020) 0.048 (0.031) 0.083*** (0.022) 0.065*** (0.013) 0.009 (0.015) 0.039* (0.022) 0.069*** (0.013) 0.062*** (0.012)

0.008 (0.277) 0.035** (0.015) 0.033 (0.029) 0.065** (0.032) 0.221* (0.117) 0.204*** (0.073) 0.156** (0.061) 0.048 (0.054) 0.018 (0.048) 0.070 (0.047) 0.083 (0.108) 0.005 (0.093) 0.006 (0.072) 0.082 (0.081) 0.103 (0.100) 0.056 (0.057) 0.012 (0.028) 0.029 (0.028) 0.058 (0.070) 0.029 (0.071) 0.067 (0.045) 0.003 (0.020) 0.043** (0.021) 0.027 (0.042) 0.023 (0.022) 0.013 (0.020)

0.086 (0.278) 0.021 (0.014) 0.037 (0.028) 0.011 (0.032) 0.339*** (0.116) 0.202*** (0.072) 0.110* (0.061) 0.034 (0.053) 0.007 (0.045) 0.041 (0.045) 0.123 (0.106) 0.056 (0.087) 0.094 (0.066) 0.006 (0.083) 0.049 (0.100) 0.040 (0.057) 0.031 (0.028) 0.003 (0.028) 0.024 (0.073) 0.027 (0.066) 0.084* (0.045) 0.010 (0.020) 0.009 (0.021) 0.000 (0.041) 0.013 (0.022) 0.025 (0.020)

0.561* (0.298) 0.052*** (0.015) 0.007 (0.030) 0.064* (0.034) 0.248* (0.135) 0.339*** (0.079) 0.178*** (0.064) 0.066 (0.055) 0.112** (0.046) 0.063 (0.047) 0.004 (0.106) 0.021 (0.091) 0.014 (0.074) 0.050 (0.089) 0.143 (0.110) 0.018 (0.059) 0.049* (0.029) 0.036 (0.030) 0.091 (0.073) 0.148** (0.072) 0.050 (0.047) 0.026 (0.021) 0.017 (0.022) 0.037 (0.045) 0.061*** (0.023) 0.060*** (0.020)

Included Included 4027 51.865 0.000

Included Included 4027 51.865 0.000

Included Included 4027 51.865 0.000

Included Included 1739 14.288 0.000

Included Included 1739 14.288 0.000

Included Included 1739 14.288 0.000

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