Treatment design, health outcomes, and demographic categories in the literature on minimum wages and health

This literature review analyzes studies from the US, Canada, the UK, and Europe from inception to April 1, 2021 and focuses on treatment designs, health outcomes, demographic categories and data issues. Study designs are classified as treatment-effect-on-the-treated (7 studies), intent-to-treat (37), and what may be called possible-effects-on-anyone (10). Treatment-effects-on-the-treated designs are best for addressing the longstanding question: does income affect health or vice versa? I argue that they are also better for estimating the overall effect of minimum wages on health. Health outcomes are grouped into seven broad categories, such as overall physiological health and behavior, and 33 narrow categories, such as self-rated health and smoking. Demographic categories include gender, race/ethnicity, and age. The preponderance of evidence suggests that studies relying on the treatment-effect-on-the-treated and possible-effects-on-anyone designs find minimum wages improve health; there is no preponderance of evidence for overall health within intent-to-treat designs. With respect to specific health outcomes and demographic categories, there is no preponderance of evidence, except for improving infant and child health. One data issue concerns whether either intent-to-treat or possible-effects-on-everyone studies are reliable given that likely more than 70 % of people in their samples earn substantially above minimum wages thereby favoring the null hypothesis. Treatment-effect-on-the-treated designs are likely the best designs, and findings are largely consistent in showing that minimum wages improve some measures of health, for example, financial anxiety.