Eligible employers are those that offer only one plan type in a given benefit year: 1) traditional HMO/PPO/POS plans (deductibles <$500, copayments of <$50 for most services, tiered copayments for medicines); 2) HSA-HDHPs without PDLs; or 3) HSA-HDHPs with PDLs. The investigators will select "full-replacement" employers that replace a traditional plan with an HSA-HDHP for all employees at a given point in time; matched comparison employers will include those that keep all employees in their prior plan.