The problem is, it wasn't entirely accurate.
Professor Sergio DellaPergola, perhaps the most well-known expert in Jewish demographics in the world today, is among those who have rebutted the reports. "It is a canard," DellaPergola told the Times of Israel this week, suggesting that the numbers widely reported were both a result of "misunderstanding" and "journalistic counterfeit."
When you look closely at the JPPI's numbers, DellaPergola's objections make sense. The report makes no bones that the number of self-identifying Jews in the world are around 14.2 million – a number DellaPergola had come to in his own work last year, published
It then, however, adds on to this a number of other people, including those with only one Jewish parent or those who identify as partially Jewish due to their family history. Some 348,000 Israeli citizens who came to Israel under the Law of Return but are not recorded as Jews are also included in the higher figure.
Traditionally, Judaism has a comparatively strict definition of who is Jewish, with halakha (Jewish religious law) requiring either that a person's mother was Jewish or that they go through a formal conversion process. Not all Jews agree with these definitions, however. The Law of Return, an Israeli legislation that allows Jews to immigrate to Israel, was amended in 1970 to allow "child and a grandchild of a Jew, the spouse of a Jew, the spouse of a child of a Jew and the spouse of a grandchild of a Jew" to enter the country, leading hundreds of thousands of non-Jews to move to Israel.
In a phone call earlier this week, JPPI president Avinoam Bar-Yosef was keen to emphasize that the higher figure included these people, who others might not consider fully Jewish, in order to help with policy discussions (the JPPI report was presented to the Israeli Cabinet on Sunday). The JPPI report argues that there were “changing patterns of Jewish identification" in the past few years, hence the use of the larger number. Indeed, a 2013 Pew study on the nature of Jewish Americans found that more and more people could be considered "partially Jewish," in part due to the shifting attitudes to intermarriage and religion.
DellaPergola's own estimates of the world's Jewish population have made a point of not including these people, noting that if "we add persons who state they are partly Jewish and non-Jews who have Jewish parents, an extended global aggregate population estimate of 17,236,850 is obtained." DellaPergola disagrees with using these broader definitions, however: "If the United States had 6.7 million holders of a doctorate, and 1 million of these hold a doctorate partly, how many Ph.D.s are there in America?" he asked in the Forward in 2013.
So when will the core Jewish population actually reach its pre-Holocaust heights? Recent estimates by Pew found that the world's Jewish population would rise by 15 percent in the next two and a half decades, compared to 35 percent for the overall global population, to reach 16.1 million in 2050. DellaPergola's research has suggested that, had the Holocaust not taken place, the global Jewish population would have been at least 26 million and possibly as much as 32 million today.