Beginning in 1995, the Census Bureau began accounting for temporary migrants in the production of its national postcensal population estimates. Since then, net legal temporary migration has been included as one of several sub-components of net international migration (NIM), along with legal immigration, refugees, net residual foreign born, emigration of legal residents, net migration from Puerto Rico, and net federal citizen migration. The temporary migration component is a net component, and is therefore equal to the number of temporary migrants who enter during a year minus the number who leave during the same period of time. The equation used to estimate NIM at time t is as follows:
NIM t-1,t = LPR t-1,t - E t-1,t + RE t-1,t + NRFBt-1,t + NT t-1,t + NPR t-1,t + NFC t-1,t
where LPR t-1,t is legal immigration during the interval from time t-1 to time t; E t-1,t represents the emigration of legal residents from time t-1 to time t; RE t-1,t represents the movement of refugees from time t-1 to time t; NRFBt-1,t is net residual foreign born from time t-1 to time t; NT t-1,t is net temporary migration from time t-1 to time t; NPR t-1,t is net migration from Puerto Rico from time t-1 to time t; and NFC represents net federal citizen migration between time t-1 to time t. (Other sub-components of NIM are discussed in other DAPE papers.)
In order to produce an estimate of net temporary migration, the Census Bureau developed criteria to identify people who were likely to be resident temporary migrants enumerated in the 1990 census. The intent was "to define a class of person that would be enumerated in the census, would have entered the country legally, would not have adjusted to permanent resident status, and very likely would return to country of origin after a limited stay, and without adjusting to legal permanent resident (immigrant) status" (Hollmann 1996, p. 1). Based on these criteria, which are outlined below, the Census Bureau estimated a temporary migrant population in the U.S. on April 1, 1990 by age, sex, race, and Hispanic origin.
Until 2000, the Census Bureau assumed a constant population stock of temporary residents. That is, the Bureau assumed that the population of temporary migrants would remain the same size as in 1990, and that their characteristics, including age, would remain the same. This assumption was based on the belief that temporary migrants, especially foreign students, leave the U.S. after a specific amount of time, but are replaced with new temporary migrants with similar characteristics, such as new groups of students. In addition, at the time the first estimates of temporary migrants were being produced, the Census Bureau was not interested necessarily in tracking a changing migration flow of temporary migrants. Instead, the concern with this population was that it "replaces itself in a way that precludes its natural aging within U.S. territory; moreover, it is highly selective with respect to the demographic variables" (Hollmann 1996, p.1). The Bureau did not want to inappropriately include temporary migrants in the cohort component model used to produce national estimates, because we could not expect that the same temporary migrant in age category x would be in category x+1 the following year.
After an estimate of the stock of temporary migrants in 1990 was produced, an estimate of the flow of this population had to be developed for incorporation into the equation for the component of annual net international migration (Hollmann 1996). During the course of a year, the legal temporary migrant population loses people to emigration, death, adjustment of status to legal permanent resident, and "adjustment" to illegal status by overstaying visa time limits or violating the terms of a visa. New temporary migrants are also added to the resident population through migration, including some individuals who return to the U.S. more than once. To maintain the constant stock of temporary migrants but express it as a migration flow, the original 1990 estimated stock was projected forward one year using life tables, and then subtracted from the end-of-year temporary migrant population distribution, which was assumed to be the same as the initial distribution. The difference was the number of deaths experienced in each age/race/sex group, and therefore the number of replacement temporary migrants needed to maintain the initial population. This number was the estimated net number of temporary migrants who were added to the U.S. population during the year. (A forthcoming memorandum will provide a detailed discussion of these methods.)
For the estimates produced between 1995 and 1999, the net temporary migration flow in the national estimates remained constant. However, the increasing number of specialty workers granted H-1B visas in the latter half of the decade demanded a reevaluation of the assumption of a constant stock of temporary residents. The H-1B visa category includes highly skilled workers who meet minimum standards of education and skills; many of these temporary workers are employed in the information technology industry. In response to a demand for specialty workers in the U.S., Congress passed legislation in the fall of 2000 that increased the cap on the number of H-1B visas to 195,000 for each of the next three fiscal years (2000 through 2002) (Dewar 2000). The H-1B limit had already been raised in 1998 from 65,000 to 115,000 workers for fiscal years 1999 and 2000, in order to relieve the backlog of temporary migrant applications. These workers were not specifically identified in the original stock estimate, and more importantly, their known growth would not have been captured by the unchanging stock.
To account for the known increase in the number of H-1B visas, a separate allowance for H-1B workers was made for the national estimates produced in 2000. This allowance was produced using methods described by Lindsay Lowell (2000) in his estimates of the H-1B population. The annual stock of H-1B workers was estimated using DOS data on annual H-1B visa issuances and subtracting estimated deaths, emigration, and adjustment to legal permanent residence (more details will be provided in a forthcoming unpublished memorandum).
Once an annual stock of H-1B workers was estimated, the annual net flow was calculated as the change in stock from one year to the next. Age, race, and Hispanic origin were imputed onto the flows using INS and 1990 sample census with modified race data. These net flows were added to the original flow from the constant stock assumption to produce a revised estimate of annual net temporary migration between 1990 and 2000.
In addition to estimates of temporary migrants for the national estimates, the Census Bureau has also estimated temporary migration for Demographic Analysis (DA). DA has been used to evaluate coverage of every decennial census since 1960, by producing independent national estimates of the U.S. population. Although temporary migrants were not included in the national estimates program until the mid-1990s, estimates of foreign students had been previously produced for Demographic Analysis population estimates. The population of foreign students in the U.S. was estimated using data from the Institute of International Education (IIE), which publishes annual counts of foreign students by country of birth. Because IIE data have no information on age, sex, race, or Hispanic origin, we allocated these characteristics based on census data on foreign born college students (see forthcoming memorandum for further discussion of these methods).
Prior to 2000, the only temporary migrants estimated for DA were foreign students. The 2000 DA estimate (released March 2001), however, added estimates of temporary migrants used in the national estimates to the foreign student estimate. The sum of the annual net flows from 1990 through 2000 of both the 1990 stock estimate and the H-1B worker estimate was added to the difference between the 2000 and 1990 foreign student populations. The resulting estimate was used as the original 2000 DA estimate (released March 2001) of temporary migrants.
The primary goal of the DAPE project was to verify the Census Bureau's population estimates for 1990 and to create an updated 2000 estimate, by reproducing each component of the estimates. In addition to correcting any errors discovered during reproduction, the DAPE teams revised the estimates to incorporate any relevant data, where possible, that may not have been available at the time the original estimates were produced.
In our case, we decided to reproduce the 1990 stock with the original algorithm first used in 1995 to estimate temporary migrants enumerated in the 1990 census. This estimate would also be used as the updated DA estimate of temporary migrants in 1990, instead of the previous method of including only foreign students from IIE data. For the 2000 update, we re-ran the 1990 algorithm with newly available 2000 data, instead of "patching" the 1990 stock estimate with separate H-1B and foreign student estimates. These estimates were used for the final DAPE results, and their production is the focus of the remainder of this paper. However, we also verified the original estimates of the annual flow of temporary migrants, H-1B specialty workers, and foreign students. While these were not used for the DAPE population estimates, we have presented the detailed methods and results of these estimates in a forthcoming memorandum for reference purposes.
1990 Stock Estimate
The population of temporary migrants in 1990 was estimated using an algorithm of criteria developed to identify people enumerated in the 1990 census who were likely to be temporary residents. The criteria used to identify these people were based primarily on temporary visa requirements, as well as on certain assumptions about the characteristics of temporary migrants.
The first criterion used was measured by the citizenship question; a temporary migrant must have been foreign born and not a naturalized citizen on April 1, 1990. In addition, temporary migrants had to have entered the U.S. relatively recently, between 1987 and 1990. The years of entry were limited to the past three years to reflect the short-term residence of most temporary migrants; temporary migrant visas range in duration from a few months to approximately three years, with extensions available in many cases. Although many temporary migrants may still reside in the U.S. legally after three years, limiting the years of entry prevented an overestimate of temporary migrants by including people who might in fact be legal permanent or illegal residents.
Any individual who did not meet the citizenship and year of entry criteria was excluded from the potential temporary migrant population. Those who did meet these criteria but who were married to a U.S. native or naturalized citizen, or who were a child or other relative of a householder who was a U.S. citizen were also excluded. The Census Bureau assumed that immediate relatives of citizens were most likely legal permanent residents instead of temporary migrants.
The remaining potential temporary migrants were subsequently tested to see if they could be classified into one of the following categories: college students, teachers and researchers, nurses, Jamaican agricultural workers, intracompany transferees, Canadian part-year residents ("snowbirds"), au pairs, and high school students. Spouses and children of these temporary migrants, with the exception of au pairs and high school students, were also included as temporary migrants. These categories were not exhaustive of all temporary visa types, but they represented what Census Bureau analysts believed to be the majority of temporary residents in the early 1990s.
College students (F-1 visas). Potential temporary migrants were first tested against the criteria for foreign college students. A foreign college student had to be enrolled in school and have at least a high school diploma.1 Because law prohibits most foreign students from taking a job while studying in the U.S., individuals were not classified as foreign college students unless they also were not working full-time. We considered someone to be not working full-time if he had either 1) not currently been in the labor force, 2) worked 20 hours or less in the preceding week, or 3) been unemployed or not at work, and his salary income during the preceding year was less than $5,000.2 The reason for the income limit of $5,000 is not clear; we assume the intention was to account for the generally lower incomes of students, but the reason for the $5,000 limit was not documented.
The DOS also issues separate temporary migrant visas (F-2s) for the spouses and children of foreign students, as it does for other classes of temporary migrants. Therefore all non-citizen spouses and children of people who were classified as college students using the above criteria were classified as college student dependents. If spouses also themselves met the criteria for college students, they were classified as college students instead of student dependents. However, if one spouse appeared to be a college student but the other was working more than 20 hours per week or had earned at least $5,000 in 1989, then neither was classified as a college student or student dependent. This prevented us from incorrectly classifying people as college students who may have actually been in the U.S. as the dependents of other temporary workers.
Teachers and researchers (J-1 visas). The remaining non-citizens entering the U.S. between 1987 and 1990 were then tested for other temporary migrant categories. Teachers and researchers represented the first category; these temporary migrants had to have at least a Master's degree. They also had to have a health diagnosing (including physicians, dentists, veterinarians, and optometrists) or post-secondary teaching occupation, or had to have worked in the hospital or college and university industry.
Nurses (H-1A visas). A nurse was required to have at least some college, as well as an occupation in health assessment and training (including nurses, pharmacists, and therapists) or health service (dental assistants, orderlies, etc.). Nurses also had to work in a hospital or nursing and personal care facilities industry.
Jamaican agricultural workers (H-2A visas). Non-citizens who were born in Jamaica and had occupations as farm workers, farm worker supervisors, marine life cultivation workers, or nursery workers were assumed to be Jamaican agricultural workers. The reason for including agricultural workers only from Jamaica is unclear.
Those who did not meet the criteria for college students, teachers and researchers, nurses, or Jamaican agricultural workers were processed through the remaining categories' criteria.
Intracompany transferees (L-1 visas). If an individual had at least a bachelor's degree, was at least 30 years old, was currently employed, and in 1989 had either no salary income or a salary income of at least $35,000, we classified him as an intracompany transferee. Intracompany transferees are primarily managers and executives of international companies, and are therefore assumed to likely be at least college graduates. The minimum age requirement appears to be arbitrary, as does the minimum salary income; $35,000 was probably assumed to be a relatively high salary at the time, but no documentation exists for this decision. While including people with incomes of $0 is peculiar, it was possibly meant to account for individuals who may have only reported income earned while living in the U.S.
Spouses and children of teachers and researchers, nurses, Jamaican agricultural workers, and intracompany transferees were assumed to be dependents of these temporary migrants, similar to student dependents. These dependents were also included in the temporary migrant population. Children who themselves met the criteria for one of these categories were classified in that category instead of as a dependent.
Non-citizens who were still not classified at this point in the algorithm processing were tested for the remaining categories: Canadian part-year residents ("snowbirds"), au pairs, and high school students.
Canadian part-year residents (B-2 visas). Householders and their relatives could be Canadian part-year residents if they were born in Canada or had a spouse who was born in Canada. The underlying assumption about these temporary migrants was that they were probably retired individuals who spent a significant part of the year living in the U.S.; therefore they (or their spouse) also must have been at least 55 years old and they could not be in the labor force. In addition to these requirements, snowbirds could not have any U.S. natives in their households. Children were classified under this category if either their householder (parent) or the householder's spouse met the snowbird criteria. Other relatives in households could either meet these criteria themselves or live with a householder who met the criteria.
Au pairs (H-2B visas). A temporary migrant who was classified as an au pair had to be a woman between the ages of 18 and 29, been born in Europe, had to have at least a high school diploma, not be a relative to the householder, and have a private household service occupation. Her householder must have been a U.S. citizen, and there had to be at least one child related to the householder less than age 12 in the household, who was assumed to be the subject of the au pair's care taking. We believe the condition that au pairs must be born in Europe may be too restrictive. In addition, we know that au pairs do not necessarily have to live with U.S. citizens, and in fact could very possibly care for children of legal permanent residents.
High school students (F-1 visas). The last temporary migrant category was high school students. To be classified as high school students, they had to be between the ages of 14 and 18, be enrolled in school, and not be related to their householder. They had to have completed ninth grade, but be less than a high school graduate. High school students also had to be living with at least one other child aged 14 to 18, and their householder had to be a U.S. citizen.
Any non-citizen who entered between 1987 and 1990 but who could not be classified in one of the above temporary migrant categories was not counted as a temporary migrant. In addition, those who were born in certain countries were also excluded from the population of temporary migrants, because we wanted to avoid identifying people who appeared to be temporary migrants but were most likely refugees. We therefore excluded anyone born in countries that were believed to be significant sending countries of refugees to the U.S.; these included the former U.S.S.R, Afghanistan, Cambodia, Laos, Vietnam, and Cuba. Data on refugees need to be examined to determine if this assumption was appropriate.
2000 Stock Estimate
The original temporary migrant estimates for 2000 were a combination of the 1990 constant stock estimate, the H-1B allowance, and the foreign student estimate, because they were produced before any 2000 census and survey data were published. The DAPE teams, however, did have access to unpublished Census 2000 Supplementary Survey and preliminary Census 2000 sample data.
We had originally planned to use the preliminary Census 2000 sample data that was processed especially for DAPE, but data on many of the necessary variables, including income, occupation, and education, were not yet available; some of these variables had not even been coded at the time. Instead, we decided to run the 1990 algorithm on C2SS data and then apply proportions by country of birth, age, sex, race, and origin to the preliminary Census 2000 data.
The Census 2000 Supplementary Survey (C2SS) was a survey conducted in 2000 of approximately 700,000 households. It was designed so results could be compared with Census 2000 results, as a test of the future American Community Survey (ACS). Because the goal of the DAPE project was to verify and update the 2000 estimates, we decided to use these newly available data and apply similar methodology to that used for 1990 to produce a new 2000 temporary migrant estimate.
The same algorithm from 1990 (described above) was applied to the C2SS data set to produce the 2000 estimate of temporary migrants for DAPE. Despite the fact that enhancements could have been made to the algorithm used to produce the 1990 estimate, the time and effort needed to accurately research and incorporate these changes were beyond the scope of the DAPE project.
Only a few adjustments were made to the original program used for the 1990 estimate. Occupation and industry codes have changed since the 1990 census, so those needed to be updated. We used available industry code crosswalks to convert industry codes; an occupation code crosswalk was not yet available, so we contacted analysts in the Industry, Occupation, and Statistical Information Branch to assist us with those conversions. Most occupations and industries were easily recoded; one exception was the 1990 code for private household service occupations, used to identify au pairs. Because this category no longer existed in 2000, we changed the code to "child care workers." Although this category includes workers in both private households and day care facilities, we believe it represents the most appropriate available occupation category. Another necessary adjustment was to the income criteria. We decided to simply adjust all salary income dollar amounts for inflation to 1999 dollars, using Consumer Price Index adjustment factors.3
Time constraints prevented the necessary research into major countries of origin for refugees during the 1990s, so we decided not to change the countries from those used for the 1990 estimate. We did extend the list, however, to include all the former republics of the Soviet Union. The final list of refugee countries for 2000 was as follows: U.S.S.R, Afghanistan, Cambodia, Laos, Vietnam, Cuba, Estonia, Latvia, Lithuania, Belarus, Moldova, Russia, Uzbekistan, Ukraine, Armenia, Azerbaijan, Georgia, Kazakhstan, Kyrgyzstan, Tajikistan, and Turkmenistan. Anyone born in these countries was excluded from the temporary migrant population in 2000.
Once we ran the algorithm and produced an estimate of temporary migrants from C2SS, we encountered some problems that forced us to change our methodology for the 2000 estimate. We intended to apply proportions of temporary migrants in C2SS to the preliminary Census 2000 sample data, but discovered that differences between the two data sets made this impossible. We calculated the proportion of non-citizens who entered between 1997 and 2000 who were temporary migrants in C2SS for each country of birth by sex by single year of age by Hispanic origin by race category.4 These proportions were then multiplied by the number of non-citizens with years of entry 1997-2000 in each of these categories in the preliminary Census 2000 sample data. All DAPE teams used the same groupings of countries of birth in their evaluations, as well as the same race categories.
Theoretically, the total number of temporary migrants in each data set should have been about the same, but the Census 2000 number was almost 300,000, or about 40 percent, lower than the C2SS number. Upon comparing the distributions of the two data sets, we discovered that the counts of non-citizens entering between 1997 and 2000 in each country/sex/age/origin/race category differed significantly between the data sets. The reason for these differences is not entirely clear, but it is likely a combination of different sample sizes, weighting differences, and the fact that the Census 2000 sample data was constructed using preliminary edits and weights. The two data sets have been found to be comparable for larger groups such as the total foreign born, but such minutely detailed breakdowns of the data had not been previously examined, and so these particular differences had not been detected.
Owing to time constraints and lack of feasible alternatives, we decided to use the C2SS estimate of temporary migrants for our 2000 update, instead of applying C2SS proportions to the preliminary Census 2000 sample data. This still left us with the problem that C2SS was a survey of households, and therefore contained no estimate for temporary migrants living in group quarters. To estimate temporary migrants in group quarters in 2000, we applied proportions of temporary migrants from the 1990 group quarters population to preliminary Census 2000 data for group quarters.
In order to estimate the 2000 group quarters temporary migrants, we calculated the proportion of group quarters non-citizens (entered between 1987 and 1990) who were temporary migrants in 1990 in each category of country of birth by sex by single year of age by Hispanic origin by race. We then multiplied these proportions by the number of non-citizens entering 1997-2000 and living in group quarters in each of the same categories from preliminary Census 2000 sample data. The resulting numbers were our new estimates of temporary migrants living in group quarters in 2000. Because we used proportions to estimate only total numbers of temporary migrants by certain demographic characteristics, we were not able to estimate the implied visa categories for temporary migrants in group quarters in 2000.
The final 2000 temporary migrant estimate was produced by summing the C2SS estimate of temporary migrants in households with the Census 2000 estimate of temporary migrants in group quarters.