Knowledge that Transforms

In a recent article in the American Economic Review, Dahl and Lochner (2012) use changes in the Earned Income Tax Credit to estimate the causal effect of family income on child achievement. Their instrumental variable (IV ) estimates imply that a $1,000 increase in income raises combined math and reading test scores by about 6 percent of a standard deviation. I document a variable coding error. Correcting this error reduces the IV estimates by 32 percent; correcting this error does not change the qualitative conclusions of the study. (JEL H24, H31, I21, I38, J13)

We propose a novel and easy-to-implement approach to detect potential overbilling based on the hours worked implied by the service codes which physicians submit to Medicare. Using the Medicare Part B Fee- for-Service (FFS) Physician Utilization and Payment Data in 2012 and 2013 released by the Centers for Medicare and Medicaid Services, we construct estimates for physicians' hours spent on Medicare beneficiaries. We find that about 2,300 physicians, representing about 3 percent of those with 20 or more hours of Medicare Part B FFS services, have billed Medicare over 100 hours per week. We consider these implausibly long hours.

Coordinated single-offer school assignment systems are a popular education reform. We show that uncoordinated offers in NYC's school assignment mechanism generated mismatches. One-third of applicants were unassigned after the main round and later administratively placed at less desirable schools. We evaluate the effects of the new coordinated mechanism based on deferred acceptance using estimated student preferences. The new mechanism achieves 80 percent of the possible gains from a no-choice neighborhood extreme to a utilitarian benchmark. Coordinating offers dominates the effects of further algorithm modifications. Students most likely to be previously administratively assigned experienced the largest gains in welfare and subsequent achievement. (JEL C78, D82, I21, I28)

We study the evolution of trade liberalization's effects on Brazilian local labor markets. Regions facing larger tariff cuts experienced prolonged declines in formal sector employment and earnings relative to other regions. The impact of tariff changes on regional earnings 20 years after liberalization was three times the effect after 10 years. These increasing effects on regional earnings are inconsistent with conventional spatial equilibrium models, which predict declining effects due to spatial arbitrage. We investigate potential mechanisms, finding empirical support for a mechanism involving imperfect interregional labor mobility and dynamics in labor demand, driven by slow capital adjustment and agglomeration economies. This mechanism gradually amplifies the effects of liberalization, explaining the slow adjustment path of regional earnings and quantitatively accounting for the magnitude of the long-run effects. (JEL F16, J23, J31, J61, O15, O19, R23)

Rothstein (2017) successfully replicates Chetty, Friedman, and Rockoff's (2014a, b)—henceforth, CFR's—results using data from North Carolina, but raises concerns about CFR's methods. We show that Rothstein's methodological critiques are invalid by presenting simulations and supplementary empirical evidence which show that (i) his preferred imputation of missing data generates bias; (ii) his “placebo test” rejects valid research designs; and (iii) his method of controlling for covariates yields inconsistent estimates of teachers' long-term effects. Consistent with the conclusions of Bacher-Hicks, Kane, and Staiger (2016) using data from Los Angeles, we conclude that Rothstein's replication study ultimately reinforces CFR's methods and results. (JEL H75, I21, J45)

Oliver Hart delivered his Prize Lecture on 8 December 2016 at the Aula Magna, Stockholm University.

This paper models the optimal search strategies of the unemployed across space to characterize local labor markets. Our methodology allows for linkages between numerous areas, while preserving tractability. We estimate that labor markets are quite local, as the attractiveness of jobs to applicants sharply decays with distance. Also, workers are discouraged from searching in areas with strong competition from other job-seekers. However, as labor markets overlap, a local stimulus or transport improvements have modest effects on local outcomes, because ripple effects in job applications dilute their impact across a series of overlapping markets. (JEL J61, J64, R23, R58)

An ongoing debate in employment policy is whether promoting small and medium enterprises creates jobs. We use the elimination of small-scale industry (SSI) promotion in India to address this question. For 60 years, SSI promotion in India focused on reserving certain products for manufacture by small and medium enterprises. We identify the consequences for employment growth, investment, output, productivity, and wages of dismantling India's SSI reservations. We exploit variation in the timing of de-reservation across products and also measure the long-run impact of national SSI policy changes using variation in pretreatment exposure at the district level. Districts more exposed to de-reservation experienced higher employment and output growth. Entrants into the de-reserved product spaces and incumbents that were previously constrained by the size restrictions drove the increase in growth. The results suggest that dismantling India's SSI policies encouraged overall employment growth. (JEL E24, L25, L53, L60, O14, O25)

Do single women avoid career-enhancing actions because these actions signal undesirable traits, like ambition, to the marriage market? While married and unmarried female MBA students perform similarly when their performance is unobserved by classmates (on exams and problem sets), unmarried women have lower participation grades. In a field experiment, single female students reported lower desired salaries and willingness to travel and work long hours on a real-stakes placement questionnaire when they expected their classmates to see their preferences. Other groups' responses were unaffected by peer observability. A second experiment indicates the effects are driven by observability by single male peers. (JEL C93, D82, J12, J16, J31)

This paper shows how to identify and estimate, using standard semi-parametric techniques, a class of dynamic games with perfect monitoring, that have been at the frontier of recent research in political economy. The empirical analysis provides novel quantitative insights into the trade-off that voters face between ideology and ability, the differences in ability and ideology among parties and states, and the differences in preferences between political candidates and voters. We analyze the consequences of term limits and quantify their relative importance. Specifically, we characterize conditions under which term limits improve voters' welfare. (JEL C57, C73, D72)