Beyond average spending: distributional and seasonal commercial insurance trends, 2012-2021.

Objectives: The annual mean spending measures typically used to study longitudinal trends mask distributional and seasonal variation that is relevant to patients' perceptions of health care affordability and, in turn, provider collections. This study describes shifts in the distribution and seasonality of plan and patient out-of-pocket spending from 2012 through 2021.

Study design: Analysis of multipayer commercial claims data.

Methods: Medical spending per enrollee was calculated by summing inpatient, outpatient, and professional services, which comprised plan payments and out-of-pocket payments (deductible, coinsurance, co-payment). To account for the long right tail of the spending distribution, enrollees were stratified by their decile of annual medical spending, and annual mean spending estimates were calculated overall and by decile. Mean spending estimates were also calculated by quarter-year.

Results: Inflation-adjusted medical spending grew most quickly among the highest decile of spenders, without proportional growth in their out-of-pocket expenses. Out-of-pocket spending increased for the majority of enrollees in our sample prior to the COVID-19 pandemic, in real dollars and as a share of total medical spending. Out-of-pocket spending was increasingly concentrated in the early months of the calendar year, driven by deductible spending, and was lower in 2020 and 2021, plausibly due to policies limiting cost sharing for COVID-19-related services.

Conclusions: Insurance is working well to protect the highest spenders at the cost of reduced insurance generosity among spenders elsewhere in the distribution. The increasing cross-subsidization among enrollees through cost-sharing design-vs premiums-is a trend to watch among rising public concerns about underinsurance and medical debt.