The Affordable Care Act has resulted in considerable competition. In a large number of markets, this has resulted in lower premiums than expected, though there is considerable variability within each metal tier. This analysis assesses the variation in premiums within markets and the effects of competition in 10 states: Alabama, Arkansas, Colorado, Maryland, Massachusetts, New York, Oregon, Rhode Island, Virginia, and West Virginia. Four of the states have fairly limited competition, while the other six were very competitive, especially in urban, more populated markets.