This dissertation studies and identifies determinants of individual health. The first chapter analyzes how the supply of medical care affects patient treatment and health outcomes, focusing on how hospitals respond to the loss of a profitable service line. This chapter provides strong evidence that hospital spillovers across service lines are empirically important and that hospitals differentiate treatment by patient payer type. Hospitals practice both revenue augmenting and cost-cutting behavior in other lines of care, targeting specific procedures and payers according to their profitability. Specifically, they increase the number of surgical procedures and perform more marginal surgeries. The effects are concentrated in medical specialtie...