In the US there are several models of insurer competition. Three major models will be discussed: (1) Medicare Advantage for the over 65 and disabled; (2) ‘Exchanges’ or ‘marketplaces’ for the under 65 (Obamacare); (3) Health plan choice within an employer setting. By comparing the three models three important questions for the regulator will be addressed: (1) How to provide appropriate incentives for purchasing individual insurance? (2) How to combat selection? (3) Are supply-side quality incentives useful (e.g. financial incentives for higher quality plans or penalties for lower quality plans)? Evidence will be discussed about the take-up of insurance, about the extent of risk selection and the impact of risk-adjustment, and about the effect of supply-side quality incentives.