The rapid rise in health insurance premiums has severely strained U.S. families and employers in recent years. This analysis of federal data finds that if premiums for employer-sponsored insurance grow in each state at the projected national rate of increase, then the average premium for family coverage would rise from $12,298 (the 2008 average) to $23,842 by 2020—a 94 percent increase. However, if health system reforms were able to slow premium growth by 1 percentage point in all states, by 2020 employers and families together would save $2,571 per premium for family coverage, compared with projected trends. If growth could be slowed by 1.5 percentage points—a target recently agreed to by a major industry coalition—yearly savings would equal $3,759. The analysis presents state-by-state data on premium costs for 2003 and 2008, as well as projections, using various assumptions, for costs in 2015 and 2020.