地方政府間的跨域服務合作契約，實務上，常見於縣、市與特別行政區域的水平組織協力模式，但相關文獻著墨於跨域合作的實證研究卻十分缺乏。2002年，佛羅里達州議會通過決議，要求州內所有的人口達100,000以上的縣、地方自治團體及縣內的特別行政區，必須因應人口需求提供都市服務，事後並須呈報跨域服務合作契約報告（Interlocal Service Delivery Agreement Report）。本研究檢驗地方政府的跨域水平合作關係，其牽涉到地理因素、跨域服務合約以及規模經濟效果等，本文試圖建構研究原創理論與假設，並以佛羅里達州為研究對象，以OLS統計模型檢驗研究假設。本研究發現，地理因素確實是地方政府選擇採用跨域服務合作契約的主要因素，除此之外，規模經濟效果以及政治考量也具有顯著的影響力。研究限制，主要在於本研究屬於一次性的、短暫性的觀察研究，而非長時間的追蹤研究， 以中央所提供的垂直面預算資源逐漸遞減的趨勢而言，未來地方政府似乎更需倚賴水平組織協力關係來取得服務的規模經濟效果。相關研究發展是可以預期的，長時間地蒐集實務資料予以分析、評判、檢討地方政府實務運作狀況，更顯意義。

Interlocal service agreements were used widely by the horizontal cooperation of counties, cities, and special districts. But there were few empirical researches estimating their horizontal cooperative relationships. In 2002, the Florida Legislature required all counties with populations of more than 100,000, and the municipalities and special districts within those counties, to assess the provision of urban services and then provided ”Interlocal Service Delivery Agreement Report”. This research intended to test the horizontal cooperative relationships of geographical factors, adoption of interlocal service agreements, and scale economics outlined by theoretical developments and our hypotheses. Our findings further supported that geographical factors indeed mattered to the adoption of interlocal service agreements. To measure the effects of scale economies, we used the ratio of the populations for the agreement counties versus the populations of independent counties as our critical test. The evidences emphasizing the adoption of interlocal service agreements did not only result from scale economies but also from political considerations or other factors. The limitation of our research only measured differences between agreement counties and independent counties rather than their changes at the long time period. In the future, the vertical financial grants sustaining for local governments will be declining because of budgetary pressures. We can expect horizontal collaborations will be emphasized more among interlocal service delivery. Therefore, more and more efforts are needed to invest empirical cumulating researches resulting from the review and direction of this type of local practice.