目標：誘發需求是否存在一直是健康經濟學領域中爭議已久的問題，本研究藉由個別醫療服務供給者的層次，分析牙醫師人口比對牙醫師行為的影響。方法：研究設計採追蹤資料型態，研究資料為1997及1998年健保申報資料，牙醫師行為觀察變項包括牙醫師之平均病人數、平均每位病患看診次數、每次看診平均申報金額、平均看診次數及平均申報金額，自變項則以鄉鎮市區為單位計算牙醫師執業地點之牙醫師人口比，分析方法為固定效果模型與工具變項。結果：牙醫師人口比增加會導致每次看診平均申報金額上升，但幅度相當小(彈性均為0.04)，平均看診人次及平均申報金額均隨牙醫師人口比的增加而降低。結論：牙醫師以增加每次看診治療密度的方式來彌補因競爭增加所帶來損失的程度很小。政策上未來應考慮牙醫師人口比增加帶來的其它結果，再評估人力或費用的相關政策。未來研究則可由需求面作分析，並探討競爭程度與牙醫師行為間是否有非線性的關係存在。

Objectives: The existence of supplier-induced demand (SID) is still frequently being debated in health economics studies. Availability of appropriate research methodologies and econometric tools is a key to solve this mystery. This study aims to investigate the effect of dentist-to-population ratio on dentists' behavior in Taiwan by focusing on the level of individual dentist. Methods: Data of this study mainly came from the 1997 and 1998 National Health Insurance Research Database. The data were analyzed using a panel-instrument approach. Results: The results show that an increase in dentist-to-population ratio causes a slight increase in mean revenue per consultation per dentist, but declines in mean number of consultations and mean revenue per month per dentist. The results imply that dentists might respond to the losses due to a greater competition by increasing treatment intensity per consultation, but the magnitude was limited. Conclusion: Compared to previous reports, our results should be more accurate since we had incorporated the case mix adjustment, and included the panel data as well as instrument variable in our analysis. We suggest that government should use incentives to improve unequal distribution of dentists. Future researches can focus on the issue of demand side and investigate the possible existence of a nonlinear relationship between the level of competition and provider behavior.

牙醫服務；誘發需求；追蹤資料；固定效果模型；工具變項

Supplier-induced Demand; Panel Data; Dental Services; Fixed-effects Model; Instrument Variable