Immigration Statistics A Story of Neglect (1985) / Chapter Skim
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Appendix B: Some Methodological Issues in Analyzing Data on Immigration
Appendix B: Some Methodological Issues in Analyzing Data on Immigration
Pages 203-254
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From page 203... ...
, the size and growth of the population of illegally resident aliens, and net flows of U.S. citizens.
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From page 204... ...
The third piece discusses the issues of imputation and treatment of missing data with particular reference to procedures of the Immigration and Naturalization Service (INS) and the presentation of data in the INS statistical yearbooks.
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From page 205... ...
Until 1981, the INS attempted to monitor the stock of resident aliens through the Alien Address Reporting system; however, reporting was widely felt to be incomplete and the system was scrapped, although resident aliens are st ill required to register changes of address with the INS. (This requirement is seldom observed, however, and the forms are not processed.
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From page 206... ...
The first method uses information on Reportable aliens located by duration of illegal residence and other simple characteristics to estimate the size and structure of the nonlegal population of the United States. The second method combines information from the Alien Address Reporting system with information on numbers of new i~u~igrants and naturalizations to estimate both the coverage of the address reporting program and the emigration of resident aliens.
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From page 207... ...
, could be applied to locations by duration. In practice, voluntary return migration, change of status' and deaths also contribute to the attrition of the population of illegal aliens, so estimates based on locations alone will underestimate the true size of
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From page 208... ...
Total locations at one month duration or more were 231,274 in 1978. If locations were 25 percent of total losses, the value of L would be 0.93 million, and the alien population present illegally in the United States for a month or
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From page 209... ...
In 1979, 245,118 deportable aliens illegally resident for a month or more were located, so if location rates remained constant the underlying population grew at 5.8 percent annually. A growth rate around 5 percent thus seems more likely than one of 10 percent.
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From page 210... ...
If duration-specific location rates were constant from year to year, population growth rates could be calculated directly from the numbers of locations in successive years, since the locations growth rates would be identical to the underly ing populat ion growth rates. Even if we wished not to as sume constant rates, we could assume a constant duration pattern for the rates and an overall growth rate to which the durat ion-spec if ic rates would be scaled.
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From page 211... ...
Data for consecutive years would also prove useful for relaxing the assumption of stability and for examining the consistency of the results. Given the limited data available, the results using location to loss ratios that fall with duration appear most plausible; with an overall location to loss ratio of 0.59 they suggest an average illegal alien population resident a month or more of 1.2 million for 1978, a figure by no means inconsistent with other empirical estimates available.
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From page 212... ...
However, the information available provides some basis for estimating the emigration of permanent resident aliens. If all recording is complete, the number of permanent residents reporting in year t+l, PR(t+l)
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From page 213... ...
The estimated value R is not an emigration rate but rather a combined emigration and death rate. The emigration element could be obtained by subtracting a death rate calculated on the basis of the age distribution of the population being considered; this death rate would probably not exceed 10 per 1~000 for the immigrant populations from most countries of orlgln.
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From page 214... ...
No systematic attempt has been made to estimate emigration from the United States on the basis of foreign census data on Americans abroad' for some very good reasons, among them difficulty of access to the data, lack of timeliness, variation in census dates, and variation in census content. However, the success of the IMILA project, coordinated by the U.N.
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From page 215... ...
In addition, tax returns count households rather than individuals, so adjustment is required on the basis of foreign census data to obtain numbers of residents abroad from numbers of tax returns.- However, the use of foreign census data, and possible combination with IRS information, can be illustrated for the case of Japan. The number of American citizens resident in Japan is available by age and sex from the 1970, 1975, and 1980 censuses.
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From page 216... ...
1981 Characteristics of Deportable Aliens Located in the Interior of the United States. Paper presented at the annual meetings of the Population Association of America, Washington, D.C.
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From page 217... ...
1980 Prel iminary Review of Existing Studies of the Number of Illegal Residents in the United States. Mimeo.
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From page 219... ...
219 TAME B-1 Estimation of Population to Loss Ratios P/L From Invocations by Duration Assuming Population to be Stable; Growth Rates of 0, 5, and 10 Percent; 1978 Durat ion d, d+n Locat ionsMidpo int rd* -rd (Years ~nDdd*
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From page 222... ...
222 TABLE B-4 Estimation of Emigration and Coverage of Alien Address Reporting System, 1959-1979: Colombia, Mexico, the Philippines, and the United Kingdom Colombia Mexico Philippines United Kingdom pRR(e+~)
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223 to CO 1 to Cal Ct o CO N .
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From page 224... ...
224 o Ct f' o to at o .
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From page 225... ...
Perhaps more than in any other area, however, the public debate on illegal immigration is founded on much smoke and little fire. It is argued, with some justification, that hard data on illegal aliens are difficult to obtain, so discussion has been based on soft data ranging from guesses or informed opinions to results of assumption-laden estimation procedures.
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From page 226... ...
ESTIMATES OF NUMBERS OF ILLEGAL ALIENS The reemergence of illegal immigration as an issue of public concern since the early 1970s has been accompanied by a number of attempts to estimate the size of the illegal population, or components of it. Some of the early attempts were little more than guesses, and we will not review them here, beyond suggesting that they could be aptly characterized as coming out of the blue (figures of l million given by INS Commissioner Farrell for March 1972 and 6-7 million for September 1974 given by INS Commissioner Chapman)
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From page 227... ...
The population by age and sex recorded by the 1960 Mexican census was projected forward to 1970 using a 1964 life table; differences by age and sex between the 1970 census population and the 1970 projected population were interpreted as emigration to the United States between 1960 and 1970, net of return migration and deaths of migrants in the United States during the period; the total obtained was 1,866,000. Legal net migration from Mexico was then estimated from data on the growth of the Mexican-born population enumerated by the 1960 and 1970 U.S.
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From page 228... ...
Standard forward projection of registered births and the population aged 0-4 in 1960 indicate a net inflow of 327,000 males and 176,000 females between the 1960 and 1970 censuses. Underregistration of births and underenumeration of the population under age 5 affect these results, and the development of suitable adjustment factors would require a major analysis of Mexican census and vital registration data, but at face value these data do not support an outflow of children of the magnitude suggested by Goldberg.
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From page 229... ...
However, it can be said that the data do not support a huge flood of Mexicans into the United States in the 1970s, nor the entry of 1.6 million illegal Mexicans in the 1960s. It should be pointed out that the Mexican censuses are conducted on a de jure basis, so short-term illegal migrants would often be included in the census counts, further clouding the conclusions that can be drawn from the data.
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From page 230... ...
Consequently, the subjective 68-percent confidence interval cited by the authors is probably too narrow, especially for the lower limit of the interval, and could be broadened to include the statistical possibility of much less than 2.9 million illegal aliens in the United States." Given the dependence of the results on the small number of households receiving social security benefits (only 2.5 percent of all households) and on the accuracy of the legal population estimate for 1973 based on adjusted 1970 census data, Lancaster and Scheuren's estimates should not be given undue weight.
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From page 231... ...
This number of excess deaths is the key to the estimates of the illegal population, which are obtained from it by assuming different death rates, different levels of death registration completeness, and different levels of enumeration completeness for illegal residents. The estimates vary widely, the lowest being obtained by assuming that all deaths to illegal residents are registered, that no illegal residents appear in the population denominators, and that illegal residents experience the mortality rates of black and other males, while the highest are obtained by assuming that 90 percent of deaths to illegal residents are registered, that 50 percent of illegal residents are included in the population denominators, and that illegals experience the death rates of white males aged 20-44 in the United States from violent causes only.
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From page 232... ...
The first element, return by the INS, is estimated using INS data on locations by duration of illegal stay for the years 1972-1977, with locations at one year or over being distributed according to the distribution reported for each entry cohort by the illegal aliens
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From page 233... ...
Of these immigrants, 61.5 percent had lived in the United States before; the study assumes all such prior residence to have been illegal and uses the reported distribution by duration of residence applied to cohorts of legal Mexican immigrants to estimate period and cohort losses to the illegal population resulting from legalization. This step seems the most problematic of the four: since the data may not represent only periods of illegal residence, the distribution obtained will be affected by cohort effects and sampling errors, and there seems to be some possibility for overlap between voluntary return as estimated in step 2 and voluntary return followed by legal immigration as estimated in step 3.
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From page 234... ...
Second, the number of legalizations is based on data of uncertain relevance from a very small sample; although the number of losses from legalization is small, only 30,000 of an estimated 1.67 million losses in 1976, they are concentrated at high durations of illegal stay and thus have considerable weight in the forward projection process. Third and most important, the estimates at short durations for 1975 and 1976 depend heavily on forward projection of losses based mainly on histories for 1972-1977.
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From page 235... ...
Thus the 519,000 can be taken, plus or minus some allowance for sampling error, as a minimum estimate of the illegal Mexican population in the United States at the end of 1978. The returned migrant population will include some returned legal migrants, but since about half these returnees had apparently worked or looked for work in the United States during 1978, and only 15 percent reported having entered the United States legally, a substantial proportion of them were probably illegal migrants who had entered the United States for seasonal summer work but had returned to Mexico for the winter.
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From page 236... ...
Warren and Passel conclude that some 2.1 million illegal aliens were recorded in the 1980 census, an estimate that is quite sensitive to the * The annual numbers of deaths were estimated by applying crude death rates calculated from 1970 census data for aliens by age and sex and U.S.
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From page 237... ...
Some other assumptions in the procedure are given little justification, although they probably have little effect on the final estimates. In summary, the estimates of coverage of the I-53 system have a substantial margin of error (the first paper in this appendix shows that, at least for the Philippines and possibly also for Mexico, overregistration of the legal alien population by the I-53 is consistent with the annual fluctuations in registration, immigration, and naturalization)
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From page 238... ...
Surviving emigrants to the United States aged 15-39, Els_3g , can then be estimated as PM Mats 39 FIS 39 M~s 39 try El s-39 cm Of cm PM - PM e c where PMC is the proportion male of the population aged 15-39 in the absence of migration, Mls_3g and Fls_3g are the number of males and females respectively enumerated by the census, cm and of are the male and female enumeration completenesses in 1980, and PMe is the proportion of males among the surviving emigrants aged 15-39. For the unknowns, PMC was estimated using assumed sex ratios at birth ranging
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From page 239... ...
The proportion male among all emigrants aged 15-39, PMe, is assumed to be 0.60 or 0.65, a range based on sex ratios among legal immigrants of 50.3 percent and an estimate derived by Warren (1982) of 55.2 percent among illegal Mexican immigrants included in the 1979 CPS.
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From page 240... ...
Once again, the sensitivity of the estimation procedure to uncertain assumptions about the underlying parameters and the nature of the data used indicate that the results must be viewed with great caution; they do, however, provide some additional empirical support for dismissing the more irresponsible and excessive guesses of the growth and size of the illegal Mexican population in the United States. Further Indications of the Size and Growth of the Illegal Population Apart from the procedures of Garcia y Griego described above, little analytic use has been made of INS data on locations of deportable aliens to draw inferences about the size and growth of the illegal immigrant population of the United States.
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From page 241... ...
Limited additional detail is available from a study of a sample of I-213 forms for 1978 covering locations of deportable aliens in the United States illegally for at least 4 days (Davidson, 1981) , giving the distribution of the aliens located for duration of illegal stay categories 4-30 days, 1~6 months, 7 months to 1 year, 1-2 years, 3-4 years, 5-6 years, and 7 or more years.
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From page 242... ...
However, the most tempting conclusions are that pressure of attempted entries has risen in 1983 and 1984 but the long-tenm illegal population has not increased much since the late 1970s; accepting the former conclusion further implies that the Border Patrol does a much better job of locating illegal aliens shortly after entry than it is generally given credit for; the latter conclusion has to be accepted unless it is believed that location rates at longer durations of illegal residence have declined at least as fast as the population has increased since the late 1970s, a belief hard to sustain since chance locations, for instance through police referrals, would be expected to reflect the underlying population size even if investigations activities did not. Some further use of the locations data can be made by considering the person years lived illegally in the United States by located Reportable
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From page 243... ...
Though no range can be soundly defended, a population of 1.5 to 3.5 million illegal aliens in 1980 appears reasonably consistent with most of the studies. Third, there is no empirical basis at present for the widespread belief that the illegal alien population has increased sharply in the late 1970s and early 1980s; the only data available on recent trends, INS records of locations of deportable aliens, in fact suggest that the population has increased little if at all since 1977, although entry attempts may have increased,
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From page 244... ...
Davidson, C.A. 1981 Characteristics of Deportable Aliens Located in the Interior of the United States.
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From page 245... ...
Robinson, J.G. 1980 Estimating the approximate size of the illegal alien population in the United States by the comparative trend analysis of age-specific death rates.
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From page 246... ...
246 u o o em Cal o ¢ Cal a' o N can o In U ~r1 U ~ P Ct ~ v a' 1 rQ so ~ a)
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From page 247... ...
to ~ a~ 1 to AL I)
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From page 248... ...
248 TABLE B-8 Estimated Mexican Emigrants by Age Group and Sex, 1960-1970 and 1970-1980, Using Variable Growth Rate Procedure ~ in thousands) Males Females Age Group 1960-1970a1970-1980a1960-1970a1970-1980a 10-14 112196-67-143 15-19 209190-48-141 20-24 89584842 25-29 6239209179 30-34 -67-19627-163 35-39 35-4225-28 40-44 -7-122745 45-49 -3056222 50-54 115-52137-43 55-59 -41-88-38-57 60-64 28242418 65-69 -56-4-434 70-74 -16-174-15 75-79 -10-74-19-81 Total 42378308-381 aThe life tables used were from the United Nat ions model life tables (UN 1982)
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From page 249... ...
a In In is ·e En Ma girl ho a)
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From page 250... ...
250 TABLE B-10 Distribut ion of Person-Years Lived by Located Deportable Aliens and Fiscal Year of Residence, 1977-1984 Durat ion Pi sca 1 Ye ar Category of Loc at ion Fiscal Year of Residence 1977 1978 1979 1980 1981 1982 1983 1984 4 days 1977404 - - - ~ ~ ~ ~ 1978- 421 - - - - - 1979- - 405 _ ~ 1980- - - 360 - - - 1981- - - - 361 - - 1982- - - - - 352 - 1983~ 1984- - - - - - 1 589 4-30 days 1977 3309 1978 57 3215 - - - - - 1979 - 56 3148 - - - - 1980 - - 38 2141 - - - 1981 - - - 39 2202 - - 1982 - - - - 41 2275 - 1983 - - - - - 49 2767 1984 - - - - - - 52 2920 1-6 months 1977 25099 - - - - - - 1978 3518 23547 - - - - - 1979 - 4232 28319 - - - - 1980 - - 3280 21948 - - - 1981 - - - 3447 23069 - - 1982 - - - - 3490 23358 - 1983 - - - - - 3408 22805 1984 - - - - - - 3224 21575 7-12 months 1977 17166 1978 8613 14355 1979 1980 1981 1982 1983 1984 - 10242 17070 8963 14938 - 11099 18498 - - 11214 18689 9985 16642 8858 14763 1 year 1977 63541 - - - - - - 1978 99493 49747 ~ ~ ~ ~ ~ ~ 1979 81527 81527 40764 - - - - 1980 63550 63550 63550 31775 - - - 1981 14609 73047 73047 73047 36524 - - 1982 - 18992 94960 94960 94960 47480 - 1983 - - 18971 94853 94853 94853 47427 1984 - - - 14911 74556 74556 74556 37278 Total ( thousand s )
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From page 251... ...
A good recent overall account can be found in the entry on "Incomplete Data" in the Encyclopedia of Statistical Sciences (Little and Rubin, 1982~. The first rule of treating missing data is that procedures must be as uniform, standardized, and well-documented as possible.
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From page 252... ...
In that way the information that would help in the interpretation of all the tables based on those particular forms would be assembled in one place. It is very important in treating missing data to know whether the data are missing at random.
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From page 253... ...
When missing blocks of data in aggregate tables are at issue, for example if a computer tape or the transmissions from one district office should be garbled or misplaced, a likelihood maximization method would be efficient and appropriate. The idea of hot deck imputation is to substitute for values missing on one record the values that occur on another record whose values have high probability of agreeing with those that are not missing.
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From page 254... ...
For cases in which few values were missing, either in absolute amounts or relative to the size of the sample, it is generally not cost-effective to adjust. Any statistical system has to deal with missing data.
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