Do differences in rates of use among managed care and Fee-for-Service Medicare beneficiaries reflect selection bias or successful care management by insurers? I demonstrate a new method to estimate the treatment effect of insurance status on health care utilization. Using clinical information and risk-adjustment techniques on data on acute admission that are unrelated to recent medical care, I create a proxy measure of unobserved health status. I find that positive selection accounts for between one-quarter and one-third of the risk-adjusted differences in rates of hospitalization for ambulatory care sensitive conditions and elective procedures among Medicare managed care and Fee-for-Service enrollees in 7 years of Healthcare Cost and Utilization Project State Inpatient Databases from Arizona, Florida, New Jersey and New York matched to Medicare enrollment data. Beyond selection effects, I find that managed care plans reduce rates of potentially preventable hospitalizations by 12.5 per 1,000 enrollees (compared to mean of 46 per 1,000) and reduce annual rates of elective admissions by 4 per 1,000 enrollees (mean 18.6 per 1,000).
We use health insurance claims data from 63 large employers to estimate the extent of price shopping for nine common outpatient services in consumer-directed health plans (CDHPs) compared to traditional health plans. The main measures of price-shopping include: (1) the total price paid on the claim, (2) the share of claims from low and high cost providers and (3) the savings from price shopping relative to choosing prices randomly. All analyses control for individual and zip code level demographics and plan characteristics. We also estimate differences in price shopping within CDHPs depending on expected health care costs and whether the service was bought before or after reaching the deductible. For 8 out of 9 services analyzed, prices paid by CDHP and traditional plan enrollees did not differ significantly; CDHP enrollees paid 2.3% less for office visits. Similarly, office visits was the only service where CDHP enrollment resulted in a significantly larger share of claims from low cost providers and greater savings from price shopping relative to traditional plans. There was also no evidence that, within CDHP plans, consumers with lower expected medical expenses exhibited more price-shopping or that consumers exhibited more price-shopping before reaching the deductible.