The average premium change between 2015 and 2016 for the lowest-cost silver plan in the Health Insurance Marketplace varied widely by state, from a 12.1% decrease in Indiana to a 41.8% increase in Oklahoma, according to a recent study by the Urban Institute. The finding is based on the premium for a 40-year-old nonsmoker. In 19 states, most people live in areas where the average premium decreased or increased by less than 5%. In 16 other states, most people live in areas where the premium increased by more than 15%. “We find that one of the most important factors associated with premium levels for the lowest-cost silver plan and premium increases between 2015 and 2016 is the amount of competition in the market as measured by the number of insurers,” the authors said. “Rating areas with more competitors tend to have lower premiums for their lowest-cost silver plans and lower premium growth; having fewer insurers competing is associated with higher premiums and premium growth.”