Wednesday, September 28, 2011

Most important predictor of reduced family size?

Which factor reduces family size the most? Below are the standardized OLS regression coefficients for a sample of whites ages 40-59:

Standardized OLS regression coefficients

Education -.23*
Income .10*
IQ .00
Church attendance .10*
Belief in God .06*
Political conservatism .06*

*p < .05, two-tail test

Education reduces fertility more than any factor. IQ has no net impact. Look at how income has a significant positive effect on family size. Not surprisingly, religiosity and conservatism are associated with more children.


  1. Strether5:32 AM

    Excellent blog. I would be extremely interested, however, in whether what the similar regression coefficients are for a younger cohort, say 30-49, if that data exists. I realize the results will mean something slightly different since people in the 40-59 group are done having children, broadly. But I wonder if income will still link up to family size for the generations currently involved in family formation, since anecdotal evidence is so strongly against it.

    Did this come from the GSS?

  2. Anonymous6:53 AM

    Education and IQ are rather-strongly correlated with each other, so shouldn't their effects on fertility be similar?

    1. Factors of religiosity and conservatism affect that correlation, because believe it or not religiosity and conservatism correlate with higher IQ. Ain't that a kicker?

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  3. Anonymous6:59 AM

    In terms of TFRs, I find the following from the 2010 Census:

    Children/woman ages 40-45 (in 2010) [Chart]
    2.68 No HS diploma
    1.90 Only a HS diploma
    1.90 2-year college degree
    1.76 4-year college degree
    1.67 Master's degree or higher

    from post Childlessness Among Gen-X women

  4. I recently had a conversation with a elderly bisexual who has been very active in the high levels of government and is, of course, very much identified with the Democratic party and higher education.

    His usually calm demeanor (reminiscent of William F. Buckley Jr.) came near the breaking point when he started to talk about Michelle Bachmann. I pointed out to him that it was the human husbandry of his mid-Atlantic elites that had caused the demographic collapse of the most educated and liberal voters compared to the human husbandry of the evangelicals.

    That's when he lost it.

  5. That's when he lost it.

    Oh to have been a fly on the wall!

    Education -.23*
    Income .10*

    How highly correlated are Education and Income? This suggests this suggests a cohort of less educated, higher income folks having an outsized number of babies, which strikes me as a little bit surprising. Could there be hidden effects here from smashing together men and women? Would the results change if we restricted it to women? Or viewed men and women separately. My guess is that education is, if anything, more highly correlated with income for men (vis-a-vis women), and less correlated with education (again vis-a-vis women). Perhaps it is the less educated women having more of the richer mens' babies... which wouldn't be entirely surprising.

  6. Thanks. So to summarize the evidence about modern birth rates:

    1) Intelligence does not reduce fertility

    There is a correlation, but it is only there because smarter people choose more schooling. And the causal factor is either the schooling itself or other personal traits that push people into more schooling but that are unassociated with intelligence. This is true not only in the General Social Survey, but also in the Wisconsin Longitudinal Survey: "Path analysis shows that the effects of IQ on subsequent family size are almost entirely indirect through education; thus education provides most of the sought-for explanation"

    2) Female education is the cause of lower fertility

    Education reduces both male and female fertility. However income boosts male fertility by reducing the male probability of lifetime childlessness. And this income effect outweighs the fertility penalty of schooling: "The results of the analysis of the NCDS show that increasing income has a significant positive effect on reproductive success in contemporary British men. This is partly offset by a negative effect on reproductive success of level of education achieved. However, the effect of income is significant even without partialing out educational differences."

  7. 3) Female education lowers fertility primarily by stemming unplanned pregnancies

    The conventional wisdom is that educated women want fewer children. This is not true. The conventional wisdom is that educated women are too busy to have children. This is not true. Education reduces fertility by increasing the probability of lifetime childlessness among women, and it does this simply by reducing accidental youth pregnancy: “We examine how completed fertility varies by women’s education, differentiating between intended and unintended births. We find that the education gradient on fertility comes largely from unintended childbearing, and it is not explained by child-bearing desires or opportunity costs, the two most common explanations in previous research."

    This might be due to ecological or social influences at college that help women avoid such accidents, or perhaps more likely, given the lack of association with intelligence, educational choices alter or reflect conscious and subsoncious female cost/benefit decisions about pregnancy (i.e. most "accidental" pregnancies are actually calculated or passively invited outcomes when women lack competing opportunities or ambitions).

  8. Was there a range restriction in this sample? I am pretty sure that IQ does affect fertility - but you need to include the extremes of IQ. Lewis Terman's old longitudinal study of high IQ Californians noted very low fertility among the women -

    But the fertility-depressing effect of IQ in the general population can rendered irrelevant, or perhaps reversed, by some types of devout religiousness - e.g. among Mormons.

  9. Jason, the educators cannot escape responsibility for the demographic collapse of their charges. It is lousy human husbandry and this irresonsibility is primarily driven by Jewish paranoia over Hitler, plain and simple. There were plenty of folks in the "WASP" establishment circa 1924 -- that evil crypto-Nazi year of immigration restriction -- who recognized this kind of responsibility.

  10. Anonymous12:38 PM

    Some data here on fertility among 'Generation X".

    Among other findings, 43% of women aged 33 to 46 do not have any children.

    It's interesting that "only" 32 percent of men in the same age bracket have no children.

  11. The general rules don't always apply. My wife and I both have graduate degrees, reasonably high IQs and six kids. I think education and low birth rate are a cultural effect rather than an IQ effect. Plato nailed it pretty well in the Symposium when he associated intellectuality with a sterile contemplation of ideas and left the reproducing to the proles.

    My wife and I are both LDS and grew up in a culture that loves children. Our religious culture was (obviously, I guess) more than enough to counter the attitudes of academia, although most of my colleagues and profs (I was a graduate student in the University of California system) seemed rather pleased that at least someone of their class was reproducing. I never got the feeling they hated kids--just didn't want to be bothered.

  12. @Fred - from my study of Mormons I would guess that your wife did not go to graduate school, but married and began the family in her early twenties?

    That seems to be the key fact to enable higher than replacement average fertility: the *norm* being that women do not pursue education beyond bachelor's level, instead marry and begin families from their early twenties.

  13. bgc--As I clearly stated, my wife and I both have graduate degrees (she has a masters), but to clarify--she got her graduate degree by going to graduate school.

    We both married in our early twenties and started having kids fairly early (while we were both in graduate school). It is not impossible to have kids and go to graduate school at the same time. It just takes hard work and a little self discipline.

  14. Fred is a perfect example of the royal scam. Worship of royalty is promoted because it gives the illusion that everything will be alright as long as we have a few making it through the selection event.

    Here's a thought experiment:

    Jew capitulates with Nazis to guard other Jews. Claims: "Hey, its not a rule that Nazi's exterminate us!"

  15. Anonymous9:22 PM

    Fred is a perfect example of the royal scam. Worship of royalty is promoted ...

    Huh? Fred worships royalty, or promotes the worship of loyalty?

  16. Anonymous10:50 PM

    Huh? Fred worships royalty, or promotes the worship of loyalty?

    I think the point is that when there is concentration or centralization of fertility, there are attempts to portray the situation as if everything is fine by pointing to the fertile, noting that "it is not impossible", that it "just takes hard work and a little self discipline", rather than as a pathological situation or environment.

  17. Anonymous6:33 AM

    That's when he lost it.

    Your elderly bissexual Democract is typical of the oddness concerning liberals. Most liberals lose it and go balistic over people like Glenn Beck and others whom are neoconservatives and libertarians which is odd because these individuals aren't even in the league of the far-right.

  18. Lucilla6:36 AM

    The general rules don't always apply.

    The exception to the rule does not become the rule. You're a lucky Mormon Fred but the vast majority of people cannot "have it all". "Having it all" is a huge feminist myth.


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