Spillover effects of Medicare fee reductions: evidence from ophthalmology.

Relatively little research has examined physicians' supply responses to Medicare fee cuts especially whether fee reductions for specific procedures have "spillover" effects that cause physicians to increase the supply of other services they provide. In this study we investigate whether ophthalmologist changed their provision of non-cataract services to Medicare patients over the time period 1992-1994, when the Medicare Fee Schedule (MFS) resulted in a 17.4% reduction in the average fee paid for a cataract extraction. Following the McGuire-Pauly model of physician behavior (McGuire and Pauly, 1991), we estimated a supply function for non-cataract procedures that included three price variables (own-price, a Medicare cross-price and a private cross-price) and an income effect. The Medicare cross-price and income variables capture spillover effects. Consistent with the model's predictions, we found that the Medicare cross-price is significant and negative, implying that a 10% reduction in the fee for a cataract extraction will cause ophthalmologists to supply about 5% more non-cataract services. Second, the income variable is highly significant, but its impact on the supply of non-cataract services is trivial. The suggests that physicians behave more like profit maximizing firms than target income seekers. We also found that the own-price and the private cross-price variables are highly significant and have the expected positive and negative effects on the volume of non-cataract services respectively. Our results demonstrate the importance of evaluating volume responses to fee changes for the array of services the physician performs, not just the procedure whose fee has been reduced. Focusing only on the procedure whose fee has been cut will yield an incomplete picture of how fee reductions for specific procedures affect physician supply decisions.