A new study by the University's Steinhardt Social Research Institute found that the number of American Jews may be as much as 20 percent higher than experts previously thought.The Institute's study, "Reconsidering the Size and Characteristics of the American Jewish Population," questions the methodology of past Jewish-population studies. Prof. Len Saxe (Heller), the Institute's director, discovered the Jewish population was not falling into the range of 5.2 million Jews, as previously indicated by the National Jewish Population Study in 2000-2001, conducted by United Jewish Communities. His calculations resulted in a number as high as 6.4 million Jews.

Saxe attributed part of the discrepancy to the difficulty of contacting young adults on landline phones and the greater probability of Orthodox Jews to answer the phone as opposed to non-Orthodox Jews.

Saxe said it's difficult to determine the number of Jews in America because they are a small minority, and reliable estimates require a sizeable sample.

This figure was culled from government-sponsored studies, most of which are available to members of the Interuniversity Consortium for Political and Social Research, of which Brandeis is a member.

In order to correct past inaccuracies, the Institute used newer methods of gathering statistics that provided a larger and more diverse sample of the general and Jewish populations. Dozens of other studies were combined to produce the figure, a practice already widely used in medical studies, Saxe said.

In the past, the NJPS survey relied on calling individuals, which accounted for an underrepresentation of Jewish young adults, as cellular phones have become more popular than landline phones within that age bracket, Saxe said. It is illegal for market researchers to call cellular phones, and mobile devices do not directly correspond to geographic location.

Prof. Jonathan Sarna (NEJS) said Saxe showed there were problems with the older study methods that were not noticed in the past.

"Everybody praised Len for radically new methodologies. That is what has gotten a lot of attention," he said.

But, he added, "I don't think this study is the last word. We've seen maximalist and minimalist studies. These issues will lead to other studies which will shed further light on the size of the American Jewish community.