Wednesday, September 30, 2009

Brief: Are Jews who marry outsiders duller?

For much of their history, Ashkenazi Jews practiced endogamous marriage, sticking mostly with their own. It was incredibly difficult to marry in, although nothing would prevent a person from leaving the group by marrying out. Given the almost exclusively white collar niche that they occupied for centuries, it is worth asking whether or not the Jews who left were duller than the ones who stayed -- perhaps they couldn't hack it as a tax farmer and moved on to being a potato farmer.

Obviously we cannot look up IQ data on Medieval Ashkenazi Jews, but we can at least look at contemporary American Jews to give us a hint. The General Social Survey asks questions about your religious preference and that of your spouse. I restricted respondents to only Jews and then looked at the mean IQ of Jews with Jewish spouses (endogamous) vs. Jews with non-Jewish spouses (exogamous). To get big sample sizes, I tried two different questions about your own religion -- what it is currently, and what it was at 16. The results are the same.

Endogamous Jews score 0.03 - 0.04 S.D. higher than exogamous Jews. That's an incredibly puny difference -- it's as if the endogamous were one-tenth of an inch taller than the exogamous on average. I looked at level of education, and that too looked similar.

But although endogamous Jews may not be much smarter than exogamous ones, they do earn more and are higher-status:

Neither group of Jews has many lower-class members, and they have the same proportion who are middle-class. However, 20% of exogamous Jews vs. 12% of endogamous Jews are working-class, and 7% of exogamous Jews vs. 17% of endogamous Jews are upper-class. As for income, both groups have similar proportions that earn less than $20K or more than $100K. However, 39% of exogamous Jews vs. 29% of endogamous Jews earn between $20K and $50K, and 26% of exogamous Jews vs. 33% of endogamous Jews earn between $50K and $100K. The median income for exogamous Jews is between $44K and $46K, while for endogamous Jews it is between $50K and $52K.

So, among contemporary Jews, those who marry within their group may not be smarter than those who leave, but they are wealthier and higher-status. Those who marry out, therefore, couldn't (or didn't want to) apply their equal level of intelligence to acquire as much material success as other Jews, and left for less competitive niches, brides with less lofty financial expectations, or something else.

Whether or not this is what happened when Ashkenazi Jews left their group to join their Eastern European host populations, we can't say for now. But it doesn't seem unreasonable -- only so many people can be high-status within a group, so the rest -- brainy or not -- will have to look elsewhere to find success. One big difference then was that wealth and status mattered a lot more for passing your genes throughout the generations, so -- if the current pattern held back then -- the endogamous Jews would have had a Darwinian advantage over the poorer ones who married out.

GSS variables used: sprel, relig, relig16, wordsum, educ, class, realinc

1 comment:

  1. *the american jewish* identity survey found that

    1) jews who were religiously jews rich & educated
    2) jews who were not religious were educated, but not as rich
    3) jews who were adherents of another religion (mostly christianity) were not rich or educated (they were also politically representative of whites)