Fuzzy RD Is IV

In a regression rite of passage, social scientists around the world link student achievement to the average ability of their schoolmates. Such regressions reliably reveal a strong association between the performance of students and the achievement of their peers. Among all Boston exam school applicants, a regression of students’ seventh-grade math scores on the average fourth-grade scores of their seventh-grade classmates generates a coefficient of about one-quarter...

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Regressions Run

We start with regression estimates of the private school earnings advantage from models with no controls. The coefficient from a regression of log earnings (in 1995) on a dummy for private school attendance, with no other regressors (right-hand side variables) in the model, gives the raw difference in log earnings between those who attended a private school and everyone else (the chapter appendix explains why regression on a single dummy variable produces a difference in means across groups defined by the dummy). Not surprisingly, this raw gap, reported in the first column of Table 2.2. shows a substantial private school premium. Specifically, private school students are estimated to have earnings about 14% higher than the earnings of other students.

The numbers that appear in parentheses ...

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The Measure of Men: Controlling Ability

Here’s an easy work-around for the ability bias roadblock: collect information on A;- and use it as a control in regressions like equation (6.3). In an effort to tackle OVB in estimates of the returns to schooling, ’metrics master Zvi Griliches used IQ as an ability control.- Without IQ in the model, Griliches’ estimate of ps in a model controlling for potential experience is.068. Griliches’ estimated short regression schooling coefficient is well below Mincer’s estimate of about 11%, probably due to differences in samples and dependent variables (Griliches looked at effects on hourly wages instead of annual earnings). Importantly, the addition of an IQ control knocks Griliches’ estimate down to pl

= ...

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Playing the Lottery

The first KIPP school in New England was a middle school in the town of Lynn, Massachusetts, just north of Boston. An old ditty warns: “Lynn, Lynn, city of sin, you never come out the way you came in.” Alas, there’s not much coming out of Lynn today, sinful or otherwise. Once a shoe manufacturing hub, Lynn has more recently been distinguished by high rates of unemployment, crime, and poverty. In 2009, more than three-quarters of Lynn’s mostly nonwhite public school students were poor enough to qualify for a subsidized lunch. Poverty rates are even higher among KIPP Lynn’s entering cohorts of fifth graders...

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Randomized Results

Randomized field experiments are more elaborate than a coin toss, sometimes regrettably so. The HIE was complicated by having many small treatment groups, spread over more than a dozen insurance plans. The treatment groups associated with each plan are mostly too small for comparisons between them to be statistically meaningful. Most analyses of the HIE data therefore start by grouping subjects who were assigned to similar HIE plans together. We do that here as well.8

A natural grouping scheme combines plans by the amount of cost sharing they require. The three catastrophic coverage plans, with subscribers shouldering almost all of their medical expenses up to a fairly high cap, approximate a no-insurance state...

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Masters of ’Metrics: Donald Campbell

The RD story was first told by psychologists Donald L. Thistlethwaite and Donald T. Campbell, who used RD in 1960 to evaluate the impact of National Merit Scholarship awards on awardees’ careers and attitudes.- As many of our readers will know, the American National Merit Scholarship program is a multi-round process, at the end of which a few thousand high-achieving high school seniors are awarded a college scholarship. Selection is based on applicants’ scores on the PSAT and SAT tests, the college entrance exams taken by most U. S. college applicants.

Successful candidates in the National Merit competition have PSAT scores above a cutoff (and have their PSAT scores validated by doing well on the SAT, taken later)...

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