Professor Garthwaite is an applied microeconomist whose research examines the effects of government policies and social phenomena with a focus on health and biopharmaceutical sectors. His recent work has focused on the private sector effects of the Affordable Care Act, including the labor supply effects of large insurance expansions, the changes in uncompensated hospital care resulting from public insurance expansions, and the responses of non-profit hospitals to financial shocks. In prior work, he has examined the impact of government cash assistance programs on health and the effect of changes in expected mortality from the emergence of crack-cocaine markets on educational attainment.

Professor Garthwaite also studies questions of pricing and innovation in the biopharmaceutical sector. In this area he has examined the effect of expanded patent protection on pricing in the Indian pharmaceutical market, the innovation response of United States pharmaceutical firms to increases in demand, and the relationship between health insurance expansions and high drug prices.