目的：本研究之目的在於驗證醫院之間的鄰近效應是否會影響醫院參加醫療品質指標計畫之意願。方法：本研究以座落於台北與高屏分局之醫院為研究對象。本研究之依變項為是否參加醫療品質指標計畫（TQIP與THIS）。透過地理資訊系統，本研究發展出距離為基礎以及行政疆界為基礎之競爭指標，包含賀芬達指數與醫院密度。醫院服務量相關變數為控制變數。本研究採用logistic迴歸進行鄰近效應之比較。結果：結果顯示醫院特性在是否參與醫療品質指標計畫間存有顯著差異。然而，經過控制相關的共變數之後，僅有病床數具有顯著差異。透過地理資訊系統，本研究共發展出十二種競爭指標。多數競爭指標在加入預測模型之後，皆具有顯著解釋力，特別是以五公里為半徑之賀芬達指數。結論：在過去研究就中有許多如何測量醫院競爭程度的討論。本研究採用兩種常見的市場範圍定義以及競爭強度定義，並去評估不同的市場競爭指數是否會影響醫院行為的實證調查。依據本研究結果，市場環境資訊是醫院行為調查研究中一項重要的因子。

Objective: The purpose of this study was to examine the relationship between the neighborhood effect and hospital's willingness to participate in quality indicator projects. Methods: A total of 238 hospitals registered in Taipei and Kao-Ping branch of Bureau of National Health Insurance, were recruited in this study. The dependent variable is whether hospital chooses to join the Taiwan Quality Indicator Project (TQIP) and Taiwan Healthcare Indicator Series (THIS). By employing geographic information system, we calculated distance-based and boundary-based competition indices (Herfindahl-Hirschman Index and hospital density). Hospital service volume was used as control variables. The logistic regression was used to compare the different definition of neighbor effect.Results: The results showed that the characteristics differed significantly between hospitals that participated in quality indicator projects and those that did not. However, after controlling for covariates, only number of beds was a significant discriminator. By employing the geographic information system, we developed twelve competition indices. Most of these, especially the Herfindahl-Hirschman Index at 5km radius, improved the model fit significantly.Conclusions: There has been considerable controversy about the appropriate measurement of hospital competition in the literature. This paper adopts the two most common definitions of hospital market area and the two most common methods of measuring the intensity of competition within an area and to assess whether different measures of hospital competition matter in empirical investigations of hospital behaviors. The results imply that the structural feature of market environment is also an important factor for understanding hospital behaviors.