Friday, December 27, 2013

What Makes a Credible Minimum Wage Study?

A study released earlier this year by the University of California's Institute for Research on Labor and Employment takes a nuanced view of recent studies which have been published about the labor-market effects of the minimum wage. 

Because minimum wage policy has recently become a highly-contentious policy issue in both the US and Europe, the academic debate has also intensified, with much of the discussion focusing on the underlying empirical methodology to be used for examination of the minimum wage. At stake is the accurate determination of the effect of minimum wage policy. 

The study considers use of spatially-related control variables to be essential, due to both structural and cyclical differences between and among states, cities, regions, and counties. A valid minimum wage study should also, according to the authors, differentiate between different segments of the labor force and should be able to measure actual effects on wages of minimum wage statutes. Overall, labor-market heterogeneity is not taken into effect as much as it should be. Failure to do so can and has clouded empirical results in minimum wage studies.

We assess alternative research designs for minimum wage studies. States in the U.S.with larger minimum wage increases differ from others in business cycle severity, increased inequality and polarization, political economy, and regional distribution. The resulting time-varying heterogeneity biases the canonical two-way fixed effects estimator. We consider alternatives including border discontinuity designs, dynamic panel data models, and the synthetic control estimator. Results from four datasets and six approaches all suggest employment effects are small. Covariates are more similar in neighboring counties, and the synthetic control estimator assigns greater weights to nearby donors. These findings also support using local area controls.
Max Berre is an economist at the EDHEC-Risk Institute (Ecole Des Hautes Etudes Commerciales du Nord) who has worked as a sovereign debt expert at the Inter-American Development Bank in Washington and has taught financial economics at Maastricht University in the Netherlands.