It’s not just Aunt Ethel’s imagination. Jews of the American West really are different from their Midwest, Southern and East Coast cousins.

That’s the conclusion reached by Steven M. Cohen, director of the Berman Jewish Policy Archive at Stanford University. After examining data from the 2013 Pew Research Center survey of American Jewry, he discovered sharp distinctions between Jews of the Pacific and Mountain states and everyone else.

“The West is the most secular part of the country and the least hospitable to ethnic perpetuation, said Cohen, who spoke last month at Stanford University in an event co-sponsored by the Taube Center for Jewish Studies. “When I went to grad school, I learned that Italian Americans in California were less ‘Italian’ than their counterparts in New York. Culturally, the West melts religious ethnic identities, so what we’re seeing among Jews is a phenomenon among comparable ethnic groups.”

That plays out in rates of assimilation, intermarriage and disaffiliation with Jewish community organizations. Cohen noted that the Pew data show these phenomena to be higher among the estimated 1.35 million Jews in the West.

Western Jews are less likely to marry Jewish spouses (17 percent vs. 32 percent elsewhere), more likely to intermarry (60 percent vs. 40 percent) but less likely to be married at all (43 percent vs. 53 percent).

For Jews in the West raising children, 40 percent do so with some exposure to Judaism, as opposed to 63 percent in the rest of the country, according to the study. It also found more Western Jews were baby boomers (ages 50-65), 35 percent vs. 29 percent elsewhere.

“That reflects migration patterns,” he said. “Because of high intermarriage rates in the West and low fertility rates, the number of younger Jews is relatively smaller compared to other parts of the country. So baby boomer Western Jews may not have produced as many Jewish children as their counterparts.”

This adds up to fewer and less cohesive Jewish neighborhoods, less affiliation with institutions such as synagogues, fewer Jewish rituals in the home and fewer Jewish holidays observed (15 percent vs. 26 percent nationally). One stat that hammers this home: Only 15 percent of Western Jews understand some prayerbook Hebrew, as opposed to 28 percent nationally.

None of this surprises Cohen, who has been examining Jewish population trends for decades. He believes his analysis should come with a couple of cautionary notes to leaders keeping a watchful eye on the future of the Bay Area Jewish community.

“One, the elderly Jewish population is going to explode,” he said. “The other is the middle-age population is going to decline.”

That’s not necessarily all bad news. “Highly educated elderly Americans have become more vital and are living longer,” he said. “That might not present so much an [elder] care challenge as an opportunity for community engagement. We are not yet fully engaging Jews in their 70s and 80s, and we need to begin to do so.”

Cohen also noted that despite lower numbers of affiliated Jews and higher assimilation rates, the Bay Area remains an entrepreneurial hotspot when it comes to new Jewish enterprises, such as Urban Adamah, Wilderness Torah, Kevah and G-dcast, all successful Jewish startups born in the Bay Area.

“The same culture that produced so much assimilation also produces innovation,” Cohen said. “The openness of Western society on the one hand softens social boundaries between Jews and non-Jews. On the other hand, it liberates and empowers creative Jews to act in unconventional and imaginative ways.”

Those are the positive takeaways. But despite the high rate of Jewish pride Pew respondents expressed across the board, Cohen is still not optimistic when he ponders the Jewish future of the Bay Area community.

He cites the famed sociologist Herbert Gans, who wrote of what he called symbolic ethnicity, meaning that American ethnic groups preserve symbolic attachments to their ancestry with no consequences, practices, associations or affiliations.

Think wearing green socks on St. Patrick’s Day.

“I believe that many Jews are in the same situation today. They know they’re Jewish, but it has no consequences on their behavior,” Cohen said. “Last year, Gans wrote about the darkness of European ethnicity. American Jews are the brightest of American ethnic groups, but the gloom is coming.”

One remedy Cohen suggests is greater outreach to non-Jews eager to live Jewish lives, either through conversion or simple self-identification.

“Jews will need to develop ways to not merely welcome non-Jews and the intermarried,” Cohen said, “but to engage and educate their non-Jewish family members. The unconventional transitions of non-Jews becoming Jewish is ever more frequent.”