Sunday, July 05, 2009

Are smart Jewish women having fewer kids? I looked at GSS data to see if high-IQ Jewish women are having fewer children than less intelligent Jews. Here are the mean number of children for women ages 40 and over for two time periods.

Mean number of children


High IQ 2.03
Low IQ 1.97


High IQ 1.88
Low IQ 2.10

The total fertility rate has slipped a bit among smart Jewish women, while it is now a bit higher for less intelligent woman. So the trend over the past four decades has been slightly dysgenic.

UPDATE: To focus on recent trends, we need a much narrower age range--let's look at women ages 40-59. This reduces our N quite a bit, but these are the tradeoffs.

Mean number of children--Jewish women ages 40-59


High IQ 2.24
Low IQ 2.44


High IQ 1.42
Low IQ 2.42

The picture that emerges when we remove older cohorts from the analysis is much more dramatic. These numbers show a much sharper dysgenic trend. The total fertility rate for smart Jewish women has dropped significantly over the past four decades, while the rate for dull women has held steady.

The mean IQ of American Jews will decline if this continues over enough generations.


  1. How much regression to the mean would you expect if the population is basically the same population?

    If there are two sisters, the slower marries and has three kids, the smarter has one, how similar would you expect the the cousins to be in such situations on a large scale assuming the slow sister marries a smart guy from within the Jewish community?

    It seems if they stay within the community, it could take a long time to be dysgenic. Maybe never.

  2. I guess my point is just that you have to see how many children the men have as well.

    Do smart Jewish men also have fewer children?

  3. Anonymous12:18 PM

    My guess is that the low-IQ Jewish women with the higher fertility rates are disproportionately Hasidic. The Hasidim have famously high birth rates, and while I don't know if there are any studies of their IQ scores many of them seem relatively dull compared to other Jews.


  4. "The mean IQ of American Jews will decline if this continues over enough generations."

    Yes, but relative to the rest of the population, they may actually pull further ahead.


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