Overpaying morbidity adjusters in risk equalization models

Risk equalization in competitive health insurance markets: Identifying healthy individuals on the basis of multiple-year low spending

Objective

To study the extent to which risk equalization (RE) in competitive health insurance markets can be improved by including an indicator for being healthy.

Study Setting/Data Sources

This study is conducted in the context of the Dutch individual health insurance market. Administrative data on spending and risk characteristics (2011‐2014) for the entire population (N = 16.6 m) as well as health survey data from a large sample (N = 387 k) are used.

Study Design

The indicator for being healthy is low spending in three consecutive prior years. “Low spending” is defined in three ways: belonging to the bottom 60%, 70%, or 80% of the annual spending distribution. Versions of the Dutch RE model 2017 with and without the indicator are compared on individual‐level payment fit and, using the survey data, group‐level payment fit.

Principal Findings

All three alternative models outperform the Dutch RE model 2017. However, significant unpriced risk heterogeneity remains. Compared with the 60% threshold, the 80% threshold comes with a larger improvement in fit but identifies a less selective group.

Conclusions

The performance of the RE model can be improved by adding an indicator for being healthy based on multiple‐year low spending. However, risk‐selection potential remains, warranting high priority to further improvement of RE.

Deriving risk adjustment payment weights to maximize efficiency of health insurance markets

Risk-adjustment is critical to the functioning of regulated health insurance markets. To date, estimation and evaluation of a risk-adjustment model has been based on statistical rather than economic objective functions. We develop a framework where the objective of risk-adjustment is to minimize the efficiency loss from service-level distortions due to adverse selection, and we use the framework to develop a welfare-grounded method for estimating risk-adjustment weights. We show that when the number of risk adjustor variables exceeds the number of decisions plans make about service allocations, incentives for service-level distortion can always be eliminated via a constrained least-squares regression. When the number of plan service-level allocation decisions exceeds the number of risk-adjusters, the optimal weights can be found by an OLS regression on a straightforward transformation of the data. We illustrate this method with the data used to estimate risk-adjustment payment weights in the Netherlands (N = 16.5 million).

Improving risk equalization with constrained regression

State-of-the-art risk equalization models undercompensate some risk groups and overcompensate others, leaving systematic incentives for risk selection. A natural approach to reducing the under- or overcompensation for a particular group is enriching the risk equalization model with risk adjustor variables that indicate membership in that group. For some groups, however, appropriate risk adjustor variables may not (yet) be available. For these situations, this paper proposes an alternative approach to reducing under- or overcompensation: constraining the estimated coefficients of the risk equalization model such that the under- or overcompensation for a group of interest equals a fixed amount. We show that, compared to ordinary least-squares, constrained regressions can reduce under/overcompensation for some groups but increase under/overcompensation for others. In order to quantify this trade-off two fundamental questions need to be answered: "Which groups are relevant in terms of risk selection actions?" and "What is the relative importance of under- and overcompensation for these groups?" By making assumptions on these aspects we empirically evaluate a particular set of constraints using individual-level data from the Netherlands (N = 16.5 million). We find that the benefits of introducing constraints in terms of reduced under/overcompensations for some groups can be worth the costs in terms of increased under/overcompensations for others. Constrained regressions add a tool for developing risk equalization models that can improve the overall economic performance of health plan payment schemes.