(See Corrections & Amplifications item below.)
A new study found that rates of marriage outside the faith were sharply curbed among young Jews who have taken "birthright" trips to Israel, a development that could hearten Jewish leaders worried about assimilation.
Fears of shrinkage among the American Jewish population heightened after studies in the early 1990s showed that more than 50% of Jews were marrying non-Jews, potentially making it more difficult to pass the religion on to offspring. Most estimates of America's Jewish population place it a little higher than six million, although some demographers have argued it is higher. The U.S. census doesn't track people by faith.
Over the past decade, Taglit-Birthright Israel, a U.S. nonprofit founded by Jewish businessmen, has sponsored nearly 225,000 young Jewish adults for free 10-day educational tours of Israel as a way to foster Jewish identity. The program is also supported by the Israeli government.
While past studies have found that trip participants return with a greater appreciation of their Jewish roots, a study to be released Monday by Brandeis University researchers is the first to suggest that the trips also affect marriage behavior. Its results showed that 72% of those who went on the trip married within the faith, compared with 46% of people who applied for the trip but weren't selected in a lottery.
Study author Leonard Saxe said the findings show that "a high-quality educational experience can alter the trajectory of young peoples' lives.…They learn they can find meaning by being part of an ethnic and religious group." Mr. Saxe is a professor of Jewish community research and social policy.
The study was partly funded by Taglit-Birthright, but Mr. Saxe said that Brandeis researchers came up with the question on marriage on their own.
Taglit's founders and funders include Charles Bronfman, heir to the Seagram liquor empire, and Michael Steinhardt, a former hedge-fund manager.
The trips are open to those ages 18 to 26, who say they are Jewish and haven't previously traveled to Israel on a study program. The program spends about $3,000 per participant, and 40,000 people applied for 10,000 spots this past summer, said Deborah Camiel, spokeswoman for the organization.
The Brandeis study looked at 1,500 non-Orthodox Jewish adults who took Taglit trips or applied for one between 2001 and 2004. The Orthodox were excluded because they were presumed to have very low interfaith marriage rates regardless of Taglit trips.
In an interview, Mr. Steinhardt, 68 years old, says the study results were encouraging, but he is concerned that education in Jewish upbringing is falling short if one trip can make such a difference in marriage behavior. "Something is very much wrong" in upbringing, he says. Mr. Steinhardt, who describes himself as an atheist, has said he supports Taglit because he wants to pass along Judaism's humanistic values.
The issue of intermarriage and how to address it is controversial within Jewish culture. Christopher Winship, a sociologist at Harvard University who converted to Judaism 15 years after marrying a Jewish spouse, says there are two competing theories for solution. One is that Jews should embrace programs that dissuade people from intermarrying; the other says intermarriages are inevitable and that welcoming intermarried couples is the best way to ensure Jewish continuity.
A study published by the Combined Jewish Philanthropies in Boston found that 60% of children in interfaith families in the greater Boston Jewish community were being raised as Jews. These findings indicated that intermarriage may not be a big threat, said Mr. Winship.
Mr. Saxe said it isn't clear why the Taglit trips may have influenced marital choices.
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Corrections & Amplifications:
Orthodox Jews were excluded from a Brandeis study on marriage behavior among young Jews who have taken "birthright" trips to Israel because Orthodox Jews were presumed to have very low interfaith marriage rates. An earlier version of this article incorrectly said they were presumed to have high interfaith marriage rates.Printed in The Wall Street Journal, page A6