Western governments have frequently come under attack for failing to control illegal immigration and for having little idea of how many unauthorized migrants are living within their borders. Unauthorized migration takes many forms such as Mexicans slipping over the border into the southern U.S., East Asian workers being transported by traffickers into Western Europe and people who enter a country legally but overstay their visa. The presence of significant numbers of unauthorized migrants within a country will adversely affect the accuracy of methods used to calculate important economic indicators including per capita income and unemployment rates. Moreover, the uncertainty about population numbers makes it difficult for governments to plan and adequately fund service provision in such areas as education, health and policing.
Researchers in many countries have attempted to develop methods for estimating numbers of unauthorized migrants in order to provide data for use in improving immigration controls and help increase the accuracy of population estimates for use in governance. However, this has proved to be a formidable task given the clandestine nature of unauthorized migration and the vested interest of such migrants in remaining hidden from the authorities. With the use of creative methods, some success has been achieved but only with large margins of error.
Legalizing Incentives
Methods of counting unauthorized migrants fall broadly into two categories: direct and indirect. Direct methods involve the use or collection of data relating specifically to this group. Particularly valuable direct data collection opportunities arise when governments implement regularization programs as occurred in the U.S. in 1986. At best, however, the data generated from such programs only provides a rough indication of numbers of unauthorized migrants since eligibility for regularization usually depends on meeting certain conditions such as a minimum residence period; moreover, it is impossible to tell what percentage of eligible applicants actually apply for regularization.
Since many unauthorized migrants will take up employment in their new country, employer surveys are another means of collecting data on them. Some employer surveys have been quite successful in generating information on the nature and distribution of illegal working. However, their use in providing information on the size of the unauthorized migrant population is limited. For one thing, illegal working is not synonymous with illegal residence – some workers may hold valid residence visas but be prohibited from employment. Moreover, some unauthorized migrants may be working in areas not covered by the surveys or may be economically inactive. Similarly, immigration enforcement data on detections of unauthorized migrants are likely to capture only a small proportion of the whole illegal population.
Creating Blanks and Filling Them In
Indirect methods of counting unauthorized migrants involve comparing different sources of data and making inferences. The “residual” statistical method has been used by both U.S. and UK government statisticians in recent years. Basically, this involves comparing census and immigration data from two different points in time relating to the foreign-born known to be resident in the country. The data is used to calculate the “residual” population, defined as the total number of foreign-born residents minus all legal immigrants and temporary legal migrants, with data adjusted for mortality and emigration over time. A small proportion of the residual population is assumed to be quasi-legal, including those awaiting the outcome of an asylum application; the remainder is defined as population of unauthorized migrants.
The residual method was used to estimate that there were approximately seven million unauthorized migrants in the U.S. in January 2001, equating to around 2.5% of the total population. Within the UK, this method was used to arrive at a central estimate of 430,000 unauthorized migrants as at April 2001 or 0.7% of the population. Both estimates were acknowledged to have very large margins of error; the UK study noted, for example, that the actual figure was likely to be anywhere within the range of 310,000 to 570,000 depending on different assumptions that could be made in the statistical model. Critics have argued that these figures vastly underestimate the true scale of unauthorized migrations; more recent U.S. studies have put the likely numbers of illegal immigrants as closer to 11 or 12 million and even as high as 20 million.
The answer to the question “Can unauthorized migrants be counted?” seems to be “Yes but not all of them.” Innovative techniques including qualitative research might be used to find out more about the characteristics of unauthorized migrants, but the shifting target of their total number within a country is likely to remain elusive and subject to debate.
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