Knowledge that Transforms

Covariate-adjusted cross-sectional comparisons show that Medicaid patients have worse health outcomes than other patients. We evaluate the validity of this research design for estimating the causal effect of Medicaid on mortality. Even after controlling for common covariates, Medicaid patients have worse preoperative health and lower socioeconomic status than privately insured patients. Controlling for additional variables shrinks the mortality differences but still does not eliminate imbalance in other predetermined variables. These results can be explained by fairly weak assumptions about unmeasured confounders. We conclude that cross-sectional observational methods do not produce valid causal estimates of Medicaid’s mortality effects.

We study how firms’ personnel practices react to labor market regulation. While a company is compelled to comply with a new law, what is the ripple effect of the change on existing personnel policies and practices? We provide evidence using passage of the Age Discrimination in Employment Act and nearly two decades of administrative data from a large US firm. In line with theory, we find a weakening of long-term implicit incentives and movement toward pay for performance. Furthermore, the data are consistent with the firm carefully managing its personnel practices according to economic principles to preserve incentives for employees.

We study the impacts of a major reform to vocational secondary education that aimed to move beyond the trade-off between providing occupational skills and closing off academic opportunities. Norway’s Reform 94 integrated more general education into the vocational track, offered vocational students a pathway to college, and increased access to apprenticeships. We identify reform impacts through a difference-in-discontinuity research design applied to linked population registries. The reform substantially increased initial vocational enrollment, but with divergent consequences by gender. Overall, the reform succeeded at improving social mobility, particularly for disadvantaged men, but it somewhat exacerbated the gender gap in adult earnings.

How does personal exposure to economic conditions affect individual human capital investment choices? Focusing on bachelor’s degree recipients, we find that cohorts exposed to higher unemployment rates during typical schooling years select majors that earn higher wages, have better employment prospects, and lead to work in a related field. Conditional on expected earnings, recessions also encourage women to enter male-dominated fields, and students of both genders pursue more difficult majors. We conclude that economic environments change how students select majors, and we find evidence that students who respond to the business cycle enjoy earnings typical of their new majors.

We analyze the consequences of labor market quotas for the wages of women in high-level positions. Labor market quotas create uncertainty about the reason a woman is promoted. Firms know whether they promoted female employees because of the quota or their ability; their competitors do not. A winner’s curse, reducing competition for women in high-level positions, results. This widens the gender pay gap for these women. Ex ante, women are better off without quotas. Next we investigate how quotas affect incentives for employers to learn women’s abilities to make better job assignment decisions. Then, under specific conditions women may benefit.

Across states, there is little correlation between a state’s marriage rate or cohabitation rate and own population. Within states, there is a positive (no) correlation between a state’s marriage (cohabitation) rate and its population growth rate. The Cobb-Douglas marriage matching function (CDMMF), which extends the Choo-Siow MMF to include peer effects, can rationalize these correlations. The model is easy to estimate. The CDMMF is estimated using panel data across US states from 1990 to 2010. The estimated model replicates the above scale effects. These effects are not sufficient to explain the large recent declines in the gains to marriage.

Survey nonresponse and attrition undermine the validity of many and possibly most econometric estimates. We propose that survey administrators and evaluators proactively create an instrument for observation, for example, by ex ante randomizing participants to differing intensity of follow-up. We illustrate how to apply our proposed methodology using a carefully conducted randomized controlled trial, the Moving to Opportunity demonstration project, which de facto randomly assigned a subset of subjects to more intensive follow-up. The approach yields treatment effect estimates similar to the unbiased estimator based on complete administrative data and has narrower confidence intervals than alternative bounding approaches.

Fewer births occur on major US holidays than would otherwise be expected. We use California data to study the nature and health implications of this birth date manipulation. We document 18% fewer births on the day of and just after a holiday. Cesarean sections account for roughly half of the decline. “Missing” holiday births are displaced to a window of time 11 days before the holiday through 16 days after the holiday. High-risk births are more likely to be rescheduled. Despite the change in timing, we find little evidence of any adverse health consequences for babies born around a holiday.

Using data for three cohorts of women in the PSID, we show that annual earnings inequality fell sharply between the late 1960s and the mid-1990s, with a large decline in the component attributable to the extensive margin. We then fit earnings-generating models that incorporate both intensive- and extensive-margin dynamics to data for the three cohorts. Our models suggest that more than 80% of the decline in female earnings inequality can be attributed to a weakening of the link between family-based factors (i.e., children and the presence and incomes of partners) and the intensive and extensive margins of earnings determination.