J Chron Dis, Vol. 31, pp. 347-352 @ Pergamon Press Ltd. 1978. Printed
0021-9681/78/0501-0347 in Great
$02.00/O
Britain
A METHODOLOGIC PROBLEM IN MORTALITY STUDIES OF MIGRANT POPULATIONS MARY MONK and M. ELLEN WARSHAUER Department
of Community and Preventive Medicine, New York Medical College, Fifth Avenue at 106th Street, New York, 10029, U.S.A. (Received in revised form 1 October 1977)
Abstract-Using US. census reports of state of birth for 1950, 1960 and 1970, we performed a cohort-analysis of black men born in New York State and in three Southern states. There were large increases from one census year to the next in the number ofmiddle-aged men reported to have been born in New York State. Conversely, there were larger than expected decreases from one census to the next in the number of men reporting the Southern states as their birth place. We believe these changes represent errors in reporting state of birth in the census. Such reporting errors will result in erroneous death rates for migrant and non-migrant populations when death certificate data and census data are used to calculate the rates. In New York City, death rates for black migrants were higher than was actually the case and those for nonmigrants lower.
Epidemiologic studies of migrants have provided tantalizing, and sometimes useful, clues to cancer etiology [l]. For example, on the basis of the first major analysis of cancer mortality among foreign-born whites in U.S.A. in 1950 [2], Haenszel suggested that stomach cancer was probably more influenced by early environmental or genetic factors and intestinal cancer by factors in the current environment. Since that time Lilienfeld et al. [3] for the period 1959-1961 found that in general the foreign-born in U.S.A. had higher cancer mortality rates than the native-born. Greenwald et al. [4] found higher rates of stomach and colon cancer among Russian-born immigrants in New York State (NYS) in 1969-1971 than among native-born whites. Mancuso and Sterling [S] reported higher rates of cancer mortality for 13 sites among non-white migrants to Ohio than among Ohio-born non-whites. Although these findings suggest that in some cancers current environmental factors may play an important role, most investigators have recognized the possibility that the mortality differences could arise because migrant status is not recorded in the same way on the death certificate as on census reports, and thus lead to erroneous mortality rates. In a study covering the 4 months after the 1960 census, place of birth on the death certificate was compared with that on the census record for the decedent [6]. There was This research was supported by a grant from the Ruth Estrin Goldberg Memorial for Cancer Research and by General Research Support Grant RR-05398 from the General Research Support Branch, Division of Research Resources. National Institutes of Health. 347
MARY MONK and M. ELLENWARSHAUER
348
a 9% disagreement between the two records with more foreign-born reported on the death certificate than on the census record. This kind of reporting error would tend to raise the mortality rates for migrants. The analysis reported here illustrates the extent of reporting errors in a study of cancer mortality among black migrants to New York City (NYC). We planned to compare, for selected gastro-intestinal cancers, the mortality of Southern-born blacks who had migrated to NYC with that of Northern-born blacks for the 5-yr periods around 1960 and 1970. Both the mortality and incidence rates for stomach and colon cancer are lower in the South than in the North. We expected to find that the rates for Southern migrants to NYC would be higher than for Southern non-migrants but lower than Northern-born blacks. METHOD
OF STUDY
AND
EARLY
FINDINGS
Death certificates in NYC, which contain data on age, sex, race and state of birth, were abstracted for native-born blacks who died in the 1960 and 1970 periods. The U.S. census [7] provides information on the age and sex of native blacks (non-whites) living in NYC according to their region of birth, including the number and percentage born in NYS. In NYC, in 1970 the census reported that close to one-third of native black men over 45 yr and living in NYC had been born in NYS, with little variation from one age group to another. Our preliminary analysis of data abstracted from death certificates showed that only about 10% of black cancer decedents had been born in NYS. In Table 1 are presented the age adjusted rates for colon and stomach cancers of NYS-born and TABLE 1. NUMBEROF DEATHSAND AGE ADJUSTEDMORTALITYRATES(PER lOO,OOO)*FOR STOMACHAND COLON CANCER,1968-1972, FORBLACKMEN IN NEW YORK CITY ACCORDING TO PLACEOF BIRTH Stomach cancer
Colon cancer
Place of birth
No.
Rate
No.
Rate
Blacks born in New York State Blacks born in South
28 289
3.6 28.5
13 106
4.5 23.7
*Indirect age adjustment using standard rates in [8].
Southern-born blacks based on death certificate and census data. Rates for the Southern migrants were five to eight times higher than for non-migrants. This, of course, was quite startling-NYS-born blacks in NYC seemed relatively immune to these cancers and, conversely, migrants were at very high risk.
ANALYSIS
OF PLACE
OF BIRTH
OF BLACKS
IN SUCCESSIVE
CENSUS
YEARS
We then looked carefully at the 1960 population of non-whites in NYC (a somewhat larger group than blacks only) and at their birthplaces. Table 2 shows for 1960 and 1970 the numbers of non-whites living in NYC and born in NYS. A comparison of these numbers for the 2 yr revealed that between 1960 and 1970 there was a sizeable increase in the number of New Yorkers born in NYS. For example, in NYC in 1960 there were
Epidemiology;
Migrants;
Death Certificates;
Death Rates
349
TABLE 2. NUMBER OF NON-WHITE (1960) OR BLACK (1970) MALES LIVING IN NEW YORK CITY AND BORN IN NEW YORK STATE,BY AGE “/,Increase
Age, yr
1960
1970
15-24 25-34 35-44 45-54 55-64 65-74 75+
30488 24452 16Y7X 8723 4832 2021 631
41119 33349 2162-i 12320 6945 2737
from 1960-70 for given age group
34.9 36.4 27.4 41.2 43.7 35.4
16,978 non-whites born in NYS in the age group 35-44; in 1970 there were 21,625 blacks born there in the age group 45-54 yr-an increase of 27.4%. Even larger increases were shown for other age groups (the % column in Table 2). We had expected that there would be decreases from 1960 to 1970 because blacks (1970) are a smaller group than non-whites (1960) and because some of the NYS born men would die in the lo-yr period. The increase we found was not accounted for by more complete reporting in 1970 than in 1960 ; non-reporting of birthplace was higher in 1970 for all age groups. There remained, of course, the possibilities that: (a) some NYS-born blacks had moved out of the city prior to 1960 and moved back between 1960 and 1970; or (b) place of birth was inaccurately reported in the census. In order to determine which was the more reasonable explanation, we turned to State @Birth census reports for 1950,1960, and 1970 [9]. For each of these years, there are tables for each state showing the number of people born in that state, no matter where the people were living at the time of the census. In a 1950 post-census enumeration survey [lo], about 3% of those reporting gave a different state of birth in the census and in the later survey. Estimates of reliability for later censuses were not available to us. Table 3 shows the number of non-white men (black men in 1970) born in NYS and still alive in U.S.A. in each census yr, according to.their age in the census yr. It is clear from this Table that the number ofNYS-born men in a given age cohort increases each successive census year and by a sizeable amount. For example, men aged 30-39 yr in 1950 and born in NYS numbered 14,240. By 1960, when the same group was 40-49 yr, there were 17,415 men (a 22% increase) and by 1970, when the group was 50-59 yr, there were 20,681, an additional increase of 19% from 1960 to 1970. There is no biologically plausible explanation for this phenomenon. It is possible, however, that the known undercounts of black men in the census, which vary by age, could account for these changes. That is, undercounts may be greatest at ages 30-39 yr and less for each succeeding decade of life, thus increasing the numbers because of more complete reporting. An examination of the national estimates of census undercounts for 1960 and i970 suggests that this explanation cannot account for all of the NYS increases [ 111. In 1960, for example, the undercounts for black men aged 40-49 yr were lo-11%; in 1970, the undercounts for black men aged 50-59 were also about lo-11%. The undercounts for men born in NYS could, of course, have been different from those for black men in the U.S.A. as a whole. In order to check this possibility further we looked at the changes in the number of
MARYMONK
350
andM.
ELLEN~ARSHAUER
TABLE 3. TOTALNUMBEROFNON-WHITE(~~~O,~~~O)ORBLACK(~~~O)MALESBORNINNEWYORKSTATE,BY AGE,ACCORDINGTOCENSUSESFORTOTALU.S.POPULATION
Age, yr
1950 Census
Born in New York State 1960 Census
20-29 30-39 40-49 50-59 60-69 70+
27690 I4240 9435 4895 2555 1455
39296 33291 /74/i 10842 5279 2823
y; Change 1960-70
1970 Census 77067 50720 38314 _70681 11676 6765
29.1 15.1 18.8 7.7 28.1
TABLE ~.TOTAL NUMBER OF NON-WHITE (1950,196O)o~ BLACK (1970)~~~~s BORN IN THREE SOUTHERN STATES,BYAGE,ACCORDINGTOCENSUSESFOR TOTAL U.S.POPULATION
Age, yr 20-29 30-39 40-49 50-59 60-69 70+ *From
1950 Census 315170 3 I6560 252615 165710 102485 57935
US. Life Table 1959-61
Southern-born 1960 Census
1970 Census
272338 285823 279353 205903 123146 75638 for non-white
272545 237096 232252 ?/O/7? 143547 87783
‘;AChange 1960-70
_ -
men in mid-yr of 1960 age group
12.9 18.7 22.6 30.3
y’, Expected to die 1960-70*
3.8 7.1 14.3 26.9
[12].
blacks born in three Southern states over the same period. The states we selected were those from which many New York blacks come-Georgia and North and South Carolina. Table 4 shows that non-white or black men born in these Southern states died (or decreased in some way) at rates much higher than expected. For example, in 1950,316560 men aged 30-39 yr were reported as natives of these states; in 1960 only 279,000 men 40-49 yr (12% less) were so reported in the census and in 1970,216,OOO men remained. Thus, 23% of the men reported to be in this group in 1960 were no longer so reported in 1970. Using 1959-61 U.S. life tables, we estimated that only about 14% of non-white males 45 yr old would be expected to die in this lo-yr period [12]. Although life expectancy for black men is somewhat lower in these Southern states [12] than in U.S.A. as a whole, this difference would not account for 58% more deaths than expected in a given decade. We looked at tables for non-white women in these states for the 3 census yr and found decreases greater than expected, but not as great as for men. DISCUSSION
We do not believe that blacks from Southern states actually died at rates so much higher than expected. Nor do we believe that there can be a real increase in the number of men born in NYS in the middle ages of life. It seems much more likely that many Southern-born men moved from the South to New York between 1950 and 1970 and in
Epidemiology
; Migrants ; Death Certificates ; Death Rates
351
the 1960 and 1970 censuses were reported as ‘born in New York State.’ A number of reasons for such reporting errors have occurred to us. First, the census information may be provided by a household member who does not know the birthplace of other members, particularly other adults. Second, the form in which the question about birthplace was asked changed from 1950 to 1960 to 1970. In 1950, a census enumerator asked directly where each person was born. In 1960, the information was sometimes asked and sometimes written in by a household member. In 1970, all the information was written in by a household member in response to the (write in).’ In (check) or question: ‘Where were you born-this State 1970 particularly, the easiest reply would be to check ‘this state’ as birthplace. It is also possible that people believe there is an advantage in being born in NYS (or in the state where they reside), for reasons of employment, welfare or social acceptance. All factors may be accentuated when a small geographic area is studied. And it is always possible that NYS or NYC census data present unique problems. Whatever the reasons, there do seem to be inaccuracies and the changes in census population estimates we found for blacks in NYC would tend to produce the very high rates for migrants, compared with non-migrants, that were shown in Table 1. This could occur, not necessarily because migrants have higher rates, but because the population estimate for them is too low and the estimate for state-born persons too high. This would not happen, of course, if the state of birth reported for the census were the same as that for the death certificate. We feel that death certificate information is likely to be more accurate; it is usually provided by a close relative in response to a spoken question and there is no obvious advantage in misstating birthplace. It is unlikely that this kind of census reporting problem occurs to the same extent for all migrant groups or in all areas. We found from an analysis of state of birth data for whites of New York that, as expected, there were decreases in successive age groups from one census yr to the next. Our conclusion from this cohort-type analysis of birthplace is that migrant studies of mortality that use census estimates of the migrant population may yield highly inaccurate results particularly for blacks or for groups in a small geographic area. If death rates for migrants are a great deal higher or consistently higher for each cause of death than rates for non-migrants, the possibility of error in census estimates should be seriously considered and attempts to verify place of birth data should be made.
REFERENCES 1. 2. 3. 4. 5. 6.
7.
Kmet J: The role of migrant population in studies of selected cancer sites-a review. J Chron Dis 23 :305-324, 1970 Haenszel W: Cancer mortality among the foreign-born in U.S.A. J Nat Cancer Inst 26:37-132, 1961 Lilienfeld A, Levin ML, Kessler II: Cancer in U.S.A. Cambridge, Harvard University Press, 1972 Greenwald P, Korns RF, Nasca PC et al.: Cancer in U.S. Jews. Cancer Res 35:3507-3512, 1975 Mancuso TF, Sterling TD: Relation of place of birth and migration in cancer mortality in U.S.A.-a study of Ohio residents (1959-1967). J Chron Dis 27:459-474, 1974 National Center for Health Statistics-comparability of marital status, nativity and country of origin on the death certificate and matching census record U.S., May-August 1960. Vital and Health Statistics, PHS No. 1000 Series 2, No. 34. U.S. Pub1 Hlth Service, Washington, USGPO, 1969 (a) U.S. Bureau of the Census--census of the population-1960. Detailed characteristics. Final report PC (1) D 34 New York. Washington, USG PO, 1962 (b) U.S. Bureau of the Census--census of the population: 1970. Detailed characteristics. Final report PC (1) D 34 New York. Washington, USGPO, 1972
352
8. 9.
10. 11. 12.
MARY MONK and M. ELLEN WARSHAUER
Duffy EA, Carroll RE: U.S. metropolitan mortality, 1959-61. PHS Publ. No. 999-AP-39, U.S. Pub1 Hlth Service, National Center for Air Pollution Control, 1967 (a) U.S. Bureau of the Census--census of the population-1950. State of birth. Special report P-E #4A., Washington, USGPO, 1953 (b) U.S. Bureau of the Census--census of the population-1960. State of birth. Special report PC (2) 2A, Washington, USGPO, 1963 (c) U.S. Bureau of the Census--census of the population-1970. State of birth. Special report PC (2) 2A, Washington, USGPO, 1973 Shryock H, Siegel JS: The methods and materials of demography. U.S. Dept. of Commerce; Bureau of the Census. Washington, USGPO, 2641, 1971 Siegel JS: Estimates of coverage of the population by sex, race and age in the 1970 census. Demography ll:l-23, 1974 National Center for Health Statistics-life tables: 1959-61, Vol. 1, U.S. Life Tables: 1959-61. Vol. 2, State life tables, 1959-61. PHS Publ. No. 1252. U.S. Pub1 Hlth Service, Washington, 1964
0021-9681/78/0501-0347 in Great
$02.00/O
Britain
A METHODOLOGIC PROBLEM IN MORTALITY STUDIES OF MIGRANT POPULATIONS MARY MONK and M. ELLEN WARSHAUER Department
of Community and Preventive Medicine, New York Medical College, Fifth Avenue at 106th Street, New York, 10029, U.S.A. (Received in revised form 1 October 1977)
Abstract-Using US. census reports of state of birth for 1950, 1960 and 1970, we performed a cohort-analysis of black men born in New York State and in three Southern states. There were large increases from one census year to the next in the number ofmiddle-aged men reported to have been born in New York State. Conversely, there were larger than expected decreases from one census to the next in the number of men reporting the Southern states as their birth place. We believe these changes represent errors in reporting state of birth in the census. Such reporting errors will result in erroneous death rates for migrant and non-migrant populations when death certificate data and census data are used to calculate the rates. In New York City, death rates for black migrants were higher than was actually the case and those for nonmigrants lower.
Epidemiologic studies of migrants have provided tantalizing, and sometimes useful, clues to cancer etiology [l]. For example, on the basis of the first major analysis of cancer mortality among foreign-born whites in U.S.A. in 1950 [2], Haenszel suggested that stomach cancer was probably more influenced by early environmental or genetic factors and intestinal cancer by factors in the current environment. Since that time Lilienfeld et al. [3] for the period 1959-1961 found that in general the foreign-born in U.S.A. had higher cancer mortality rates than the native-born. Greenwald et al. [4] found higher rates of stomach and colon cancer among Russian-born immigrants in New York State (NYS) in 1969-1971 than among native-born whites. Mancuso and Sterling [S] reported higher rates of cancer mortality for 13 sites among non-white migrants to Ohio than among Ohio-born non-whites. Although these findings suggest that in some cancers current environmental factors may play an important role, most investigators have recognized the possibility that the mortality differences could arise because migrant status is not recorded in the same way on the death certificate as on census reports, and thus lead to erroneous mortality rates. In a study covering the 4 months after the 1960 census, place of birth on the death certificate was compared with that on the census record for the decedent [6]. There was This research was supported by a grant from the Ruth Estrin Goldberg Memorial for Cancer Research and by General Research Support Grant RR-05398 from the General Research Support Branch, Division of Research Resources. National Institutes of Health. 347
MARY MONK and M. ELLENWARSHAUER
348
a 9% disagreement between the two records with more foreign-born reported on the death certificate than on the census record. This kind of reporting error would tend to raise the mortality rates for migrants. The analysis reported here illustrates the extent of reporting errors in a study of cancer mortality among black migrants to New York City (NYC). We planned to compare, for selected gastro-intestinal cancers, the mortality of Southern-born blacks who had migrated to NYC with that of Northern-born blacks for the 5-yr periods around 1960 and 1970. Both the mortality and incidence rates for stomach and colon cancer are lower in the South than in the North. We expected to find that the rates for Southern migrants to NYC would be higher than for Southern non-migrants but lower than Northern-born blacks. METHOD
OF STUDY
AND
EARLY
FINDINGS
Death certificates in NYC, which contain data on age, sex, race and state of birth, were abstracted for native-born blacks who died in the 1960 and 1970 periods. The U.S. census [7] provides information on the age and sex of native blacks (non-whites) living in NYC according to their region of birth, including the number and percentage born in NYS. In NYC, in 1970 the census reported that close to one-third of native black men over 45 yr and living in NYC had been born in NYS, with little variation from one age group to another. Our preliminary analysis of data abstracted from death certificates showed that only about 10% of black cancer decedents had been born in NYS. In Table 1 are presented the age adjusted rates for colon and stomach cancers of NYS-born and TABLE 1. NUMBEROF DEATHSAND AGE ADJUSTEDMORTALITYRATES(PER lOO,OOO)*FOR STOMACHAND COLON CANCER,1968-1972, FORBLACKMEN IN NEW YORK CITY ACCORDING TO PLACEOF BIRTH Stomach cancer
Colon cancer
Place of birth
No.
Rate
No.
Rate
Blacks born in New York State Blacks born in South
28 289
3.6 28.5
13 106
4.5 23.7
*Indirect age adjustment using standard rates in [8].
Southern-born blacks based on death certificate and census data. Rates for the Southern migrants were five to eight times higher than for non-migrants. This, of course, was quite startling-NYS-born blacks in NYC seemed relatively immune to these cancers and, conversely, migrants were at very high risk.
ANALYSIS
OF PLACE
OF BIRTH
OF BLACKS
IN SUCCESSIVE
CENSUS
YEARS
We then looked carefully at the 1960 population of non-whites in NYC (a somewhat larger group than blacks only) and at their birthplaces. Table 2 shows for 1960 and 1970 the numbers of non-whites living in NYC and born in NYS. A comparison of these numbers for the 2 yr revealed that between 1960 and 1970 there was a sizeable increase in the number of New Yorkers born in NYS. For example, in NYC in 1960 there were
Epidemiology;
Migrants;
Death Certificates;
Death Rates
349
TABLE 2. NUMBER OF NON-WHITE (1960) OR BLACK (1970) MALES LIVING IN NEW YORK CITY AND BORN IN NEW YORK STATE,BY AGE “/,Increase
Age, yr
1960
1970
15-24 25-34 35-44 45-54 55-64 65-74 75+
30488 24452 16Y7X 8723 4832 2021 631
41119 33349 2162-i 12320 6945 2737
from 1960-70 for given age group
34.9 36.4 27.4 41.2 43.7 35.4
16,978 non-whites born in NYS in the age group 35-44; in 1970 there were 21,625 blacks born there in the age group 45-54 yr-an increase of 27.4%. Even larger increases were shown for other age groups (the % column in Table 2). We had expected that there would be decreases from 1960 to 1970 because blacks (1970) are a smaller group than non-whites (1960) and because some of the NYS born men would die in the lo-yr period. The increase we found was not accounted for by more complete reporting in 1970 than in 1960 ; non-reporting of birthplace was higher in 1970 for all age groups. There remained, of course, the possibilities that: (a) some NYS-born blacks had moved out of the city prior to 1960 and moved back between 1960 and 1970; or (b) place of birth was inaccurately reported in the census. In order to determine which was the more reasonable explanation, we turned to State @Birth census reports for 1950,1960, and 1970 [9]. For each of these years, there are tables for each state showing the number of people born in that state, no matter where the people were living at the time of the census. In a 1950 post-census enumeration survey [lo], about 3% of those reporting gave a different state of birth in the census and in the later survey. Estimates of reliability for later censuses were not available to us. Table 3 shows the number of non-white men (black men in 1970) born in NYS and still alive in U.S.A. in each census yr, according to.their age in the census yr. It is clear from this Table that the number ofNYS-born men in a given age cohort increases each successive census year and by a sizeable amount. For example, men aged 30-39 yr in 1950 and born in NYS numbered 14,240. By 1960, when the same group was 40-49 yr, there were 17,415 men (a 22% increase) and by 1970, when the group was 50-59 yr, there were 20,681, an additional increase of 19% from 1960 to 1970. There is no biologically plausible explanation for this phenomenon. It is possible, however, that the known undercounts of black men in the census, which vary by age, could account for these changes. That is, undercounts may be greatest at ages 30-39 yr and less for each succeeding decade of life, thus increasing the numbers because of more complete reporting. An examination of the national estimates of census undercounts for 1960 and i970 suggests that this explanation cannot account for all of the NYS increases [ 111. In 1960, for example, the undercounts for black men aged 40-49 yr were lo-11%; in 1970, the undercounts for black men aged 50-59 were also about lo-11%. The undercounts for men born in NYS could, of course, have been different from those for black men in the U.S.A. as a whole. In order to check this possibility further we looked at the changes in the number of
MARYMONK
350
andM.
ELLEN~ARSHAUER
TABLE 3. TOTALNUMBEROFNON-WHITE(~~~O,~~~O)ORBLACK(~~~O)MALESBORNINNEWYORKSTATE,BY AGE,ACCORDINGTOCENSUSESFORTOTALU.S.POPULATION
Age, yr
1950 Census
Born in New York State 1960 Census
20-29 30-39 40-49 50-59 60-69 70+
27690 I4240 9435 4895 2555 1455
39296 33291 /74/i 10842 5279 2823
y; Change 1960-70
1970 Census 77067 50720 38314 _70681 11676 6765
29.1 15.1 18.8 7.7 28.1
TABLE ~.TOTAL NUMBER OF NON-WHITE (1950,196O)o~ BLACK (1970)~~~~s BORN IN THREE SOUTHERN STATES,BYAGE,ACCORDINGTOCENSUSESFOR TOTAL U.S.POPULATION
Age, yr 20-29 30-39 40-49 50-59 60-69 70+ *From
1950 Census 315170 3 I6560 252615 165710 102485 57935
US. Life Table 1959-61
Southern-born 1960 Census
1970 Census
272338 285823 279353 205903 123146 75638 for non-white
272545 237096 232252 ?/O/7? 143547 87783
‘;AChange 1960-70
_ -
men in mid-yr of 1960 age group
12.9 18.7 22.6 30.3
y’, Expected to die 1960-70*
3.8 7.1 14.3 26.9
[12].
blacks born in three Southern states over the same period. The states we selected were those from which many New York blacks come-Georgia and North and South Carolina. Table 4 shows that non-white or black men born in these Southern states died (or decreased in some way) at rates much higher than expected. For example, in 1950,316560 men aged 30-39 yr were reported as natives of these states; in 1960 only 279,000 men 40-49 yr (12% less) were so reported in the census and in 1970,216,OOO men remained. Thus, 23% of the men reported to be in this group in 1960 were no longer so reported in 1970. Using 1959-61 U.S. life tables, we estimated that only about 14% of non-white males 45 yr old would be expected to die in this lo-yr period [12]. Although life expectancy for black men is somewhat lower in these Southern states [12] than in U.S.A. as a whole, this difference would not account for 58% more deaths than expected in a given decade. We looked at tables for non-white women in these states for the 3 census yr and found decreases greater than expected, but not as great as for men. DISCUSSION
We do not believe that blacks from Southern states actually died at rates so much higher than expected. Nor do we believe that there can be a real increase in the number of men born in NYS in the middle ages of life. It seems much more likely that many Southern-born men moved from the South to New York between 1950 and 1970 and in
Epidemiology
; Migrants ; Death Certificates ; Death Rates
351
the 1960 and 1970 censuses were reported as ‘born in New York State.’ A number of reasons for such reporting errors have occurred to us. First, the census information may be provided by a household member who does not know the birthplace of other members, particularly other adults. Second, the form in which the question about birthplace was asked changed from 1950 to 1960 to 1970. In 1950, a census enumerator asked directly where each person was born. In 1960, the information was sometimes asked and sometimes written in by a household member. In 1970, all the information was written in by a household member in response to the (write in).’ In (check) or question: ‘Where were you born-this State 1970 particularly, the easiest reply would be to check ‘this state’ as birthplace. It is also possible that people believe there is an advantage in being born in NYS (or in the state where they reside), for reasons of employment, welfare or social acceptance. All factors may be accentuated when a small geographic area is studied. And it is always possible that NYS or NYC census data present unique problems. Whatever the reasons, there do seem to be inaccuracies and the changes in census population estimates we found for blacks in NYC would tend to produce the very high rates for migrants, compared with non-migrants, that were shown in Table 1. This could occur, not necessarily because migrants have higher rates, but because the population estimate for them is too low and the estimate for state-born persons too high. This would not happen, of course, if the state of birth reported for the census were the same as that for the death certificate. We feel that death certificate information is likely to be more accurate; it is usually provided by a close relative in response to a spoken question and there is no obvious advantage in misstating birthplace. It is unlikely that this kind of census reporting problem occurs to the same extent for all migrant groups or in all areas. We found from an analysis of state of birth data for whites of New York that, as expected, there were decreases in successive age groups from one census yr to the next. Our conclusion from this cohort-type analysis of birthplace is that migrant studies of mortality that use census estimates of the migrant population may yield highly inaccurate results particularly for blacks or for groups in a small geographic area. If death rates for migrants are a great deal higher or consistently higher for each cause of death than rates for non-migrants, the possibility of error in census estimates should be seriously considered and attempts to verify place of birth data should be made.
REFERENCES 1. 2. 3. 4. 5. 6.
7.
Kmet J: The role of migrant population in studies of selected cancer sites-a review. J Chron Dis 23 :305-324, 1970 Haenszel W: Cancer mortality among the foreign-born in U.S.A. J Nat Cancer Inst 26:37-132, 1961 Lilienfeld A, Levin ML, Kessler II: Cancer in U.S.A. Cambridge, Harvard University Press, 1972 Greenwald P, Korns RF, Nasca PC et al.: Cancer in U.S. Jews. Cancer Res 35:3507-3512, 1975 Mancuso TF, Sterling TD: Relation of place of birth and migration in cancer mortality in U.S.A.-a study of Ohio residents (1959-1967). J Chron Dis 27:459-474, 1974 National Center for Health Statistics-comparability of marital status, nativity and country of origin on the death certificate and matching census record U.S., May-August 1960. Vital and Health Statistics, PHS No. 1000 Series 2, No. 34. U.S. Pub1 Hlth Service, Washington, USGPO, 1969 (a) U.S. Bureau of the Census--census of the population-1960. Detailed characteristics. Final report PC (1) D 34 New York. Washington, USG PO, 1962 (b) U.S. Bureau of the Census--census of the population: 1970. Detailed characteristics. Final report PC (1) D 34 New York. Washington, USGPO, 1972
352
8. 9.
10. 11. 12.
MARY MONK and M. ELLEN WARSHAUER
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