Angrist’s PhD thesis examined whether serving in the army negatively affected people’s future income. This is trickier to estimate than it may seem. Simply comparing the wages of people who served in the army against those who didn’t would not be evidence of a causal relationship, since people who enter the army may differ in important ways from those who don’t, and these differences may in turn affect their income potential. What is really needed is a source of randomization which takes a group of men and forces some of them into the army.
Just such a randomization tool was provided in the 1970s by the American government, which ran televised draft lotteries (
wiki) during the Vietnam War to select young men to be inducted into the army. This process essentially placed otherwise similar men into a treatment group (those who were drafted) and a control group (those who weren’t) by randomly selecting birth days of the year ranging from 1 to 366 (February 29 was included).
By combining the birth records of those born in 1950-53 with later earnings data drawn from a 1% sample of all social security numbers, Angrist found that, among white men, drafted veterans went on to earn 15% less than their peers who had avoided the army.
.. Since Pennsylvania did not change its minimum wage, this makes it the control group. If we consider New Jersey and Pennsylvania to be comparable, then we would have expected to see Pennsylvania’s downwarding sloping trend replicated in New Jersey if New Jersey had not increased its minimum wage. But we don’t see this; in fact there is a slight increase in the average number of employees in New Jersey restaurants. The authors interpret this as showing that the rise in the minimum wage did not reduce employment. Further studies on this topic are reviewed
here by Schmitt
.. They found that 7-year old Muslims whose pregnancies overlapped with Ramadan performed worse in maths, reading and writing than comparable Muslim children born to mothers where Ramadan fell soon after birth. These effects were largest (0.08 standard deviations) when Ramadan overlapped with the first three months of gestation, possibly reflecting the importance of biological processes during that time, and/or greater levels of fasting compliance among pregnant Muslim women who may have been unaware that they were pregnant.
.. They find that exposure to the famine in the prenatal environment predicted higher adult rates of obesity, diabetes and schizophrenia.