A 1990 study of winter births claimed compulsory school laws improved test scores, increased later earnings, improved health and lengthened life. It was nonsense, based on assumptions that weren’t true and never investigated.

Children born in the winter months already have a few strikes against them. Study after study has shown that they test poorly, don’t get as far in school, earn less, are less healthy, and don’t live as long as children born at other times of year. Researchers have spent years documenting the effect and trying to understand it. —Wall Street Journal

Joshua Angrist of the Massachusetts Institute of Technology and Alan Krueger of Princeton University wrote the original paper. The problem isn’t so much that they missed blatantly obvious and critical data —which they surely did— it is that the tiny differences in tests, earnings, health and lifespans were translated in government enforcement.

It is accepted as truth in government circles that compelling longer amounts of school is good for people; that making children stay in educational institutions more time is ‘for their own good’. Krueger is now an assistant Treasury Secretary, and Angrist is writing books about verifiable social measurements.

“Variation in education that is related to season of birth arises because some individuals, by accident of date of birth, are forced to attend school longer than others because of compulsory schooling. . . .

Our results provide support for the view that students who are compelled to attend school longer by compulsory schooling laws earn higher wages as a result of their extra schooling.” —Does Compulsory School Attendance Affect Schooling and Earnings? Joshua Angrist & Alan Krueger; emphasis in original

Yet the foundation of their studies is rotten. Angrist and Krueger assumed the backgrounds of children born in the winter are the same as children born in other seasons; therefore something external happens to ‘winter-babies’ that accounts for poor outcomes.

Then, a gigantic “Oops!” when a couple of other researchers found a single overlooked factor . . . the babies’ mothers.

While researching sibling behavior, Daniel Hungerman noticed that families tended to have seasonal births. Unrelated to that, Kasey Buckles —in an office across the hall from Hungerman— was investigating multiple births, and found an apparent pattern between birth seasonality and mothers’ education.

While chatting together, the two realized they may have found a significant answer to “Why ‘winter-babies’ have poor outcomes”. After reviewing data on almost every US birth over a dozen years they found an answer: ‘Winter babies’ have statistically poorer and more disadvantaged outcomes because they have statistically poorer and more disadvantaged beginnings.

The percentage of babies born to teenage, unwed, teenage, and high-school dropout mothers peaks in January every year. We know (statistically) that children of teenage mothers do less well in school, have poorer health, lower incomes, and reduced lifespans compared to the general population. We know the same is (statistically) true of children of unwed mothers, and the same is also true (statistically) of HS dropout mothers. Yet all three factors coincide and peak in January of each year.

When economics giant Daniel Hamermesh selected Buckles and Hungerman’s paper for an upcoming conference presentation he said

“I love the paper. It means you have to think about things more than you want to think.”

It also means people —or the government— shouldn’t act on the basis of assumed facts.

Sunday, September 27th, 2009 at 3:12 pm.
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