The Demographic Study of Jews is Difficult
Scholars, community leaders, and the public-at-large often inquire about the size, make-up, and location of the diverse Jewish population. There are methodological, definitional, ideological and political reasons why we do not have accurate counts of Jews around the world. Some of these factors apply to specific countries and some apply to overall efforts to count Jews. Some are unique to Jewish demography, and some are more universal issues affecting any census, specifically, or counting racial, ethnic, or religious groups. The demographic study of Jews is difficult for a variety of reasons.
Some countries do not survey religion
Some countries, like the United States, do not ask about religion in their census counts of the population. A number of interest groups (especially many Jewish organizations) are concerned about the separation of church and state, and do not want the government inquiring about religion. Therefore, we rely on a variety of surveys to try to estimate the Jewish population, including the number of diverse Jews. Many are unreliable.
Some Jewish communities are highly dispersed
Even in communities with significant Jewish populations, people are more likely to be scattered among the general population than in previous generations. Jews in the United States also live in the suburban fringes of many metropolitan areas, far from any Jewish population center, making them difficult to locate. Finding Jews to respond to surveys outside major metropolitan areas is an even more needle-in-a-haystack endeavor.
Some Jews do not want to be found
Some Jews may hide their identity or background from survey takers or a government census. The Institute for Jewish & Community Research conducted methodological tests that confirm that there are many Jews that refuse to reveal their identity. We took known lists of Jews and asked them about their religion and found that many denied that they were Jewish. Some groups of Jews are more reluctant than others to reveal their religious identity. This includes those who tend to mistrust governments; those who have been victims of persecution; those who reject their religious identity; and those who think of themselves as ethnic Jews rather than religious Jews.
Many people do not know their Jewish heritage
Finding Jews in the United States is a simple task when compared to finding individuals and groups with Jewish ancestry in some countries around the world. The sophisticated methods of survey research do not apply, and written records sometimes do not exist in some communities. Oral traditions or ritual practice are the indicators of Jewish roots and help find some people. Others do not know about their religious origins, especially those descended from ancient, but now assimilated Jewish communities. For example, many descendents of Spanish and Portuguese Jews have no idea about their Jewish ancestry.
We do not look for some Jews
Some of the problems in counting Jews result from where we look and for whom we look when we do surveys. Some of these issues cause minor shifts in the total numbers, and others can cause huge differences. Some communities, such as the Lemba of South Africa and the Ibo of Nigeria are omitted entirely. For example, when we count Jews in South Africa, we traditionally count Jewish descendants from Europeans who settled there. We do not look for and count the Lemba, an indigenous people who have practiced Judaism for centuries. Nor do we look in Uganda for black African Jews where the Abayudaya practice Judaism. Many of the official counts in most of sub- Saharan Africa, are of non-indigenous populations only, a strong statement about who is a Jew and who is not.