According to the American Jewish Identity Survey 2001, which was conducted by the Center for Jewish Studies at the Graduate Center of the City University of New York, 1 million households affiliate with a congregation; this is up from 880,000 households a decade ago.
Another 1 million Jews report they are affiliated with a noncongregational organization, such as a Jewish community center.
At the same time, the number of "core Jews" -- people who consider themselves Jewish by parentage or upbringing, but do not necessarily practice Judaism -- has declined from 5.5 million to 5.3 million people.
And the number of people who are of Jewish parentage but who identify themselves as members of other religions, a subcategory of people not counted within the core Jew rubric, has increased from 625,000 to nearly 1.5 million.
Multiple factors, including intermarriage, were cited as the reason for these changes. Even though the rate of intermarriage, 51 percent, has remained steady over the past decade, the study's authors noticed an increase of "core Jews" who intermarry -- 33 percent, up from 28 percent in 1990.
The Reform movement, which reaches out to intermarried families more actively than Conservative or Orthodox communities, has benefited most from the affiliation increase. In 1990, 35 percent of affiliated households were Reform; the study found that in 2001, that number had increased to 41 percent.
The study, which was based on a random sampling of 1,668 Jews, replicated some methodology and questions from the larger National Jewish Population Survey 1990.