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What do the numbers mean?

Figuring out Jewish population counts is notoriously complex. Depending on who is included or excluded, estimates can vary substantially

Dr Jonathan Boyd

Determining how many Jews live in a particular place is often rather more complicated than it first appears. The challenge is all about where you choose to draw boundaries – who you include as Jewish in your counts, and who you exclude. And the bottom line is that Jews themselves differ on inclusion and exclusion criteria, so there is no single agreed definition of who is a Jew. 

According to halacha (Jewish law), to be recognised as a Jew one either needs to be born to a Jewish mother or to have converted to Judaism. But even that simple definition can become highly contentious. What if someone has converted to Judaism under the auspices of an authority that some Jews do not accept? What if the Jewish status of the mother is uncertain or contested? What if someone is born to a Jewish mother, but has subsequently gone on to renounce their Jewishness or convert to another religion? 

There is no way to overcome these issues universally and conclusively. So demographic work begins by focusing on self-definition – if someone reports that they are Jewish, demographers tend to assume that they are. The most common numbers used to determine the size of a given Jewish population draw on data from censuses, surveys, community registers and administrative lists where individuals have reported conclusively that they consider themselves to be Jewish. Sometimes they tell us that by answering ‘Jewish’ to a question about their religion. Sometimes they do so in a question about their ethnicity or their culture. Sometimes they simply answer ‘yes’ to a survey question that asks ‘are you Jewish?’ 

The numbers produced by this method generate what is referred to in Jewish demography as the ‘core Jewish population.’ It is similar to the number of people who are Jewish according to halacha, but not identical. Some people who self-identify as Jewish would not be regarded as such by some religious authorities. Equally, some people who would be regarded as Jewish according to halacha choose not to self-identify. Nevertheless, this is the best and most commonly used definition; in most instances, the core Jewish population count should be considered as the ‘go-to’ estimate. 

However, Jewish demography has developed three other approaches for estimating Jewish population size, using three different inclusion criteria. The first of these is known as the ‘population with Jewish parents.’ In this instance, everyone within the core Jewish population is included, but so is anyone born to at least one Jewish parent – mother or father – who considers themselves to be partly Jewish. This population measure is quite a recent addition to Jewish demographic analysis and was developed in response to the desire within parts of the Jewish community to be more open and inclusive to the growing number of people who have this partial relationship to Jewishness due to their mixed parentage. At a time when inclusion has become an important value, there are strong voices maintaining that such people should be seen as wholly part of the Jewish population. 

2021 UK Census envelopes

For similar reasons, the third definition that is used is the ‘enlarged Jewish population.’ In simple terms, and with some minor additions, this includes all those already mentioned plus anyone who lives in their households, irrespective of whether they are Jewish. So, to give an example, imagine a household in which a Jew is married to a non-Jew, and they have chosen not to bring up their two children as Jewish. Even though three people in this family would not self-identify as Jewish, all four of them would be included within this definition. Why might that count be important? In day-to-day terms, such a family might choose to engage with the organised Jewish community for any number of purposes, including health provision, elderly care and bereavement support, so there are good grounds for including all of them when trying to assess the size of the population that might require community services of some kind. And again, if inclusion or outreach are important values, the enlarged Jewish population is an important measure. 

The final definition that demographers have developed is based on the Israeli Law of Return. Soon after the State of Israel was established in 1948, the Israel government passed legislation giving any Jew in the world the right to acquire Israel citizenship. Many countries have similar laws allowing those with an ethnic or historic connection to a nation state to become citizens. In Israel’s case, the fact that the Jewish historical experience is littered with examples of Jews being expelled from countries, denied entry or having their citizenship questioned or repealed, the case for such a law was perhaps all the more evident. However, for such a law to be enacted, it was necessary to determine the criteria by which someone could be determined Jewish. The details of those criteria have been discussed at length and amended since the legislation was first passed, but the current definition includes any person born to a Jewish mother or who converted to Judaism under the auspices of any Jewish religious authority, who does not have another religious identity. However, critically, it also extends its provisions to those people’s children, grandchildren and their respective Jewish or non-Jewish spouses, making it the most expansive definition of the four outlined here. 

Each of the four definitions expands the size of the Jewish population in turn. At a global level, the population with Jewish parents is about 33% larger than the core Jewish population, the enlarged Jewish population is about 50% larger, and the Law of Return population about 66% larger. But in some countries, the differences between these counts are much greater. In Russia, for example, where years of religious suppression under communism made it very difficult for Jews to live Jewish lives, the population with Jewish parents is estimated at over twice the size of the core Jewish population, the enlarged Jewish population at three times the size, and the Law of Return population at about four times. 

Each of these definitions has its place and its purpose. For most general purposes, the core count is the correct one to use, but there are numerous specific instances where one of the other three would be more appropriate. Decisions about which estimate to use should be driven by the specific issue that needs to be understood in each case.

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Dr Jonathan Boyd

Executive Director

Dr Jonathan Boyd

Executive Director

Jonathan has been Executive Director of JPR since 2010, having previously held research and policy positions at the JDC International Centre for Community Development in...

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