Oscar A. Mitnik

Nonparametric Tests for Treatment Effect Heterogeneity

In this paper we develop two nonparametric tests of treatment effect heterogeneity. The first test is for the null hypothesis that the treatment has a zero average effect for all subpopulations defined by covariates. The second test is for the null hypothesis that the average effect conditional on the covariates is identical for all subpopulations, that is, that there is no heterogeneity in average treatment effects by covariates. We derive tests that are straightforward to implement and illustrate the use of these tests on data from two sets of experimental evaluations of the effects of welfare-to-work programs.

Comparing Treatments across Labor Markets: An Assessment of Nonexperimental Multiple-Treatment Strategies

We study the effectiveness of nonexperimental strategies in adjusting for comparison group differences when using data from several programs, each implemented at a different location, to compare their effect if implemented at alternative locations. First, we adjust for individual characteristics differences simultaneously across all groups using unconfoundedness-based and conditional difference-in-difference methods for multiple treatments. Second, we adjust for differences in local economic conditions and stress their role after program participation. Our results show that it is critical to have sufficient overlap across locations in both dimensions and illustrate the difficulty of adjusting for local economic conditions that differ greatly across locations.

A Top-Down Approach to Stress-Testing Banks

We propose a simple, parsimonious, and easily implementable method for stress-testing banks using a top-down approach that captures the heterogeneous impact of shocks to macroeconomic variables on banks’ capitalization. Our approach relies on a variable selection method to identify the macroeconomic drivers of banking variables as well as the balance sheet and income statement factors that are key in explaining bank heterogeneity in response to macroeconomic shocks. We perform a principal component analysis on the selected variables and show how the principal component factors can be used to make projections, conditional on exogenous paths of macroeconomic variables. We apply our approach, using alternative estimation strategies and assumptions, to the 2013 and 2014 stress tests of medium- and large-size U.S. banks mandated by the Dodd-Frank Act, and obtain stress projections for capitalization measures at the bank-by-bank and industry-wide levels. Our results suggest that accounting for bank heterogeneity yields expected capital shortfalls that can be over 30 percent larger than in the case where heterogeneity is ignored. Furthermore, we find that while capitalization of the U.S. banking industry has improved in recent years, under reasonable assumptions regarding growth in assets and loans, the stress scenarios continue to imply sizable deterioration in banks’ capital positions.

The Effects of Female Labor Force Participation on Obesity

This paper assesses whether a causal relationship exists between recent increases in female labor force participation and the increased prevalence of obesity amongst women. The expansions of the Earned Income Tax Credit (EITC) in the 1980s and 1990s have been established by prior literature as having generated variation in female labor supply, particularly amongst single mothers. Here, we use this plausibly exogenous variation in female labor supply to identify the effect of labor force participation on obesity status. We use data from the National Health Interview Survey (NHIS) and replicate labor supply effects of the EITC expansions found in previous literature. This validates employing a difference-in-differences estimation strategy in the NHIS data, as has been done in several other data sets. Depending on the specification, we find that increased labor force participation can account for at most 19% of the observed change in obesity prevalence over our sample period. Our preferred specification, however, suggests that there is no causal link between increased female labor force participation and increased obesity.

Stress Testing Banks: Whence and Whither?

This paper provides a brief overview of the recent practice of stress testing banking institutions, focusing on capital adequacy. We argue that stress testing has been successfully used to mitigate bank opacity; quantify systemic risk under extreme but plausible stress; keep the participants mindful of severely adverse shocks, thereby mitigating “disaster myopia” and concomitant financial instability; and improve the data collection and analytical capabilities of financial institutions. Our paper then reviews several critiques of stress testing made by policymakers and academics. We also propose several modifications of the current stress-testing practice, such as the fusion of liquidity and capital adequacy stress testing, expansion of granular data availability, and explicit modeling of sectors inextricably connected to banking as well as the feedback mechanisms from these sectors. Addressing these issues is likely to keep stress testing highly relevant for promoting financial stability in the future.