Analyses will compare changes in outcomes from baseline to up to three years of follow-up among 1) asthma patients switched to HSA-HDHPs without PDLs from traditional plans vs. matched patients whose employers remain in traditional plans; and 2) patients switched to HSA-HDHPs with PDLs from traditional plans vs. matched controls remaining in traditional plans. The investigators will use separate regression models to compare year-to-year changes for each intervention group relative to its matched control group, rather than including all patients in a single model with multiple interaction terms.