Contrary to popular belief, numbers are not always "just numbers." As social scientists point out, many official statistics released by government agencies reflect the culture and history of the country in which they are generated. All aspects of a data collection system—from what data are collected, to the questions asked on surveys and censuses, even to what data are ultimately analyzed and disseminated—are influenced by this same context. Thus, official statistics actually embody socio-cultural influences that can prove to be problematic when attempting to compare data from different countries.
Like other official numbers, international migration statistics also reflect the culture and history of the country in which they are generated. Throughout the world, countries demarcate their national identities by defining what seem to be immutable migration-related concepts, such as "migrant," "immigrant," or "citizen," in distinct ways. This variability has a direct impact on the way the governments of those countries collect, process, and present migration data—and on the ability of data users to make direct comparisons among countries.
Models of Citizenship: Jus Soli and Jus Sanguinis
The influence of socio-cultural norms and historical experiences on migration statistics is best illustrated in the similar-yet-different concepts of "foreign born" and "foreigner," both of which are rooted in and reflect very different models of citizenship. In general, the majority of people around the world acquire citizenship in one of two ways: "by birth" (jus soli) or "by blood" (jus sanguinis). Although these are "ideal types," they remain useful in explaining the divergent outcomes of citizenship policies. In a jus soli system, citizenship is based on place of birth. Although there are exceptions to this rule, in general, people born in these countries are citizens, while people born outside are non-citizens. Thus, in a jus soli context, the term "foreign born" refers to residents of a country who were born in another country. Foreign-born residents can, under certain circumstances, change their status and become citizens through naturalization. When combined, both place of birth and citizenship status can be used to divide the population into three categories—native-born citizens, foreign-born citizens, and non-citizens—and define who among the foreign born has acquired the full rights and responsibilities bestowed on all citizens.
In a jus sanguinis system, descent and heritage play a pivotal role in defining who is, and can become, a citizen. Where people were born is not as important as if and how they can trace their ancestry back to the origin country. In this context, the term "foreigner" refers to those in the population whose heritage cannot be traced back to the host country. In general, under jus sanguinis citizenship policies, it is often difficult—though not impossible—for foreigners to naturalize, even if they are long-term residents or were native born to the country. Those foreigners who do naturalize typically have to demonstrate that they meet the required "integration" criteria, such as language skills or knowledge of the country's culture and history. While it is often difficult for resident foreigners to naturalize, it is usually easier for foreign-born ethnics to obtain citizenship after immigrating back to their ancestral "homeland," in some cases even if their families have lived abroad for generations. In this sense, the concept of foreigner divides a country's resident population—and, indeed, the world's population—into two groups: nationals, who have the right of citizenship by virtue of their ancestry, and foreigners, who must earn the right to naturalize.
Foreign Born v. Foreigner: Reflecting Alternative Views of Citizenship
These outlines of jus soli and jus sanguinis citizenship policies are, as noted, ideal types. In fact, most countries, while generally emphasizing one or the other, have increasingly blurred the distinction between the two by including elements of both in their broader procedures. However, the preeminence of either a "by birth" or "by blood" citizenship policy simultaneously reflects and defines how a country views "membership" and who does, and does not, belong. This, in turn, influences how individuals in a country's population are classified administratively and how they are counted in official statistics.
The influence of varying citizenship policies on migration statistics can be clearly seen when data from the United States and Germany are put side-by-side. Two examples will be presented here, with the first focusing on "stock" data and the other on "flow" data. Both the United States and Germany data discussed in these examples are available in The Source's Global Data Center.
Stock data represent "snapshots" of a population at a single point in time by counting (as in a census) or estimating (as in a survey) the distribution of that population according to some characteristic, such as age, income, or sex. An example of stock data would be the distribution of all foreign persons in a population by their country of origin. However, who is included in the category of "foreign persons" will depend on whether the dominant citizenship policy of a country is jus soli or jus sanguinis.
In the United States, where the citizenship policy is predominantly jus soli, "foreign persons" refers to all foreign born in the resident population and includes both naturalized citizens and non-citizens. In Germany, where a jus sanguinis policy dominates, "foreign persons" generally refers to anyone in the resident population who is a non-citizen and not of German descent, that is, both foreign-born and native-born foreigners who have not naturalized. However, it does not include either ethnic Germans who were born abroad and were awarded citizenship after immigration or non-German foreign-born persons who have naturalized; these individuals are considered to be, or to have become, nationals. As a result, while the concepts of foreign born and foreigner initially appear similar, they actually categorize people in fundamentally different ways. This makes it difficult to compare directly the migration stock data of the United States and Germany.
A similar problem exists when attempting to compare flow data. Flow data are collected and produced by governmental administrative agencies. Unlike stock data, they are collected continuously but are usually presented in an aggregate form for a point in time, such as monthly or annual statistics. A good example of flow data is the number of immigrants entering a country, since immigration is a process that occurs continuously and is catalogued year-round. Depending on whether the citizenship policy of a country is predominantly jus soli or jus sanguinis, the term "immigrant" can include very different categories of people.
In the United States, immigrant inflow data include foreign-born persons who are non-citizens entering the country for lawful permanent residence. In Germany, immigrant inflow data also include foreign-born persons who are non-citizens entering the country legally, but not all foreign born are considered immigrants. Specifically, Aussiedler, or ethnic Germans born in eastern Europe and the former Soviet Union, who meet certain requirements, have the right to enter Germany virtually as citizens. While they are enumerated in the inflow data, the Aussiedler are not considered immigrants but rather "returning nationals." This orientation also helps to explain why German citizens who have returned to Germany after long-term stays abroad are also included in the inflow data. In the United States, immigrant inflow data documents the arrival of the foreign born, while in Germany it documents both the arrival of the foreign population and the "return" of ethnic nationals.
Implications for the Comparability of International Migration Data
While it is generally assumed that statistics passively and objectively reflect the event or process they measure, in reality, they do so subjectively—in the context of the history and culture of the society in which they are produced. These socio-cultural influences can be seen in the varied concepts, legal definitions, and administrative classifications used to generate and report migration data— and this variation means that international migration statistics are often difficult to compare. Concepts and terms that may initially appear to include the same categories of people, such as "foreign born" and "foreigner" or even "immigrant," may actually encompass very different groups. This means that the rate and trend statistics generated from these data, such as "percentage of foreign persons in the total population" or "annual number of immigrants," are often not directly comparable.
Do these differences mean that comparative analyses of international migration trends and levels should not be pursued? Of course not. Fortunately, many governments recognize the problems associated with these differences and, encouraged by support from various international agencies, are moving their statistics in the direction of greater comparability. However, change takes time and, as of today, there are still migration-related concepts and terms that remain problematic in an international context. It is therefore essential for users to be aware of the existence of differences and to make every effort to understand how those differences affect the comparability of the data. This is important, because it is the degree of comparability that will determine the qualifications associated with any conclusions drawn.
Aleinikoff, T. Alexander and Douglas Klusmeyer (eds.) (2000) From Migrants to Citizens: Membership in a Changing World. Washington, DC: Carnegie Endowment for International Peace.
Aleinikoff, T. Alexander and Douglas Klusmeyer (eds.) (2001) Citizenship Today: Global Perspectives and Practices. Washington, DC: Carnegie Endowment for International Peace.
Aleinikoff, T. Alexander and Douglas Klusmeyer (eds.) (2002) Citizenship Policies for an Age of Migration. Washington, DC: Carnegie Endowment for International Peace.
Starr, Paul (1987) "The Sociology of Official Statistics." Pp. 7-57 in William Alonso and Paul Starr (eds.), The Politics of Numbers. New York: Russell Sage Foundation.