TY - BOOK AU - Cicala,Steve AU - Lieber,Ethan M.J. AU - Marone,Victoria ED - National Bureau of Economic Research. TI - Cost of Service Regulation in U.S. Health Care: Minimum Medical Loss Ratios T2 - NBER working paper series PY - 2017/// CY - Cambridge, Mass. PB - National Bureau of Economic Research N1 - April 2017; Hardcopy version available to institutional subscribers N2 - A health insurer's Medical Loss Ratio (MLR) is the share of premiums spent on medical claims. The Affordable Care Act introduced minimum MLR provisions for all health insurance sold in fully-insured commercial markets, thereby capping insurer profit margins, but not levels. While intended to reduce premiums, we show this rule creates incentives analogous to cost of service regulation. Using variation created by the rule's introduction as a natural experiment, we find claims costs rose nearly one-for-one with distance below the regulatory threshold: 7% in the individual market, and 2% in the group market. Premiums were unaffected UR - https://www.nber.org/papers/w23353 UR - http://dx.doi.org/10.3386/w23353 ER -