Educational Research - the Ethics and Aesthetics of Statistics

7 To Frame the Unframable: Quantifying Irregular Migrants’ Presence 101
is then used to identify the probability of an individual being caught by the police.
Again, a number of problematic assumptions are at work. First, the population has to
be homogeneous (with respect to the risk of being caught). This can be met through
the use of an appropriate regression method, which accounts for determined features
for apprehension, such as age, sex and origin. Second, there has to be a more or less
stable chance of getting caught. The supposition that no major policy changes take
place during the time span of the research is thus required. But most problematic
is the third and final assumption: the population under consideration has to remain
constant during the period of research. Such stability is highly unlikely as there are
peaks in flows of irregular migration (e.g. seasonal workers). This leads researchers
to make the decision to exclude certain groups from the study (Pinkerton et al.,
2004).
As a final example of estimation methods, demographic methods start from the
idea that rates concerning e.g. birth, mortality and hospitalisation are normally distributed
over the total population. Legal and illegal people are thus supposed to
experience these events to the same extent. Proportions of irregular migrants’ hospitalisations,
deaths and births are then extrapolated to estimate total numbers. The
practical advantage of these methods lies in the wide availability of the required
data, which means that there is no need to acquire new datasets. However, the
assumption that these demographic rates are similar for illegal and legal residents
can be questioned. In some populations, the birth rate is very high (e.g. Roma
population, Ringold, Orenstein, & Wilkens, 2005). Irregular migrants often live
in worse conditions than natives and are more susceptible to health problems. A
larger risk of disease due to poverty and bad living conditions may thus lead to an
over-representation of data. Furthermore, there are registration problems. Irregular
migrants are often very mobile and may choose to return due to impending demographic
risks (e.g. chronic illness, death). Sometimes, things may be the other way
around: people come here to enjoy medical care that is lacking in the country of
origin. Finally, differing benefits in the health-care system may lead to serious
underestimations. Irregular migrants are not always hospitalised when required,
because they cannot rely on the same benefits or they are afraid to profit from them
due to their illegal residence status.
7.3 Counting the Uncountable: Some Conceptual Problems
Social scientists generally acknowledge the problems resulting from various estimation
methods. They are therefore reluctant to identify estimates, and differ over
the degree of reliability that they are willing to attribute to these numbers. Problems
of measurement evidently follow from the fact that irregular migration is resistant
to registration and statistical description (Tapinos, 1999). Estimating the numbers
of illegal residents in a country is almost impossible given the fact that the phenomenon
is a grey zone. Nevertheless, a great deal of pressure is put on researchers