廿一世紀是老年人的世紀。根據衛生福利部的統計，台灣高齡人口於1993年9月達到148萬人，約佔總人口的7.1%，已超過聯合國世界衛生組織所訂定的7%指標，正式成為一個「高齡化社會（ageing society）」。然從1993年以後，高齡人口便不斷的增加，到2002年底時，台灣高齡人口已突破200萬人，台灣將進一步成為「高齡社會（aged society）」。使用DEA方法對於台灣護老機構進行績效評估，並且考量不可控制環境變數對於機構之影響方向。實證結果顯示，第四階段之效率估計值較第一階段低，顯示未考量不可控制環境因素前，護老機構的績效值有嚴重被高估之現象。排除不可控制環境因素後的CCR平均值為0.605，表示仍有40%之經營改善空間；但若未考慮不可控制因素之影響，縣市政府的CCR效率平均值為0.951，有5%的改善空間。

21 century is the century of aged people. According to the Ministry of Health and Welfare, the elderly population in Taiwan have been reached 1.48 millions, accounting for 7.1% of the total population, it exceeds the 7% standard of United Nations World Health Organization. Taiwan officially became "aging society". However, since year 1993, the elderly population continuously increased and has exceeded for 2 millions, Taiwan already becomes "aged society".DEA is a method to evaluate external uncontrollable environment factors for juding nursing homes of their financial performance. The empirical result shows that the efficiency of fourth stage is lower than first stage. It means financing performance of nursing homes have been over evaluated. Excludes uncontrollable environmental factors, average CCR becomes 0.605. It means there are 40% operating improvement of nursing home can be get. But without considering effects of uncontrollable environmental factors, average of CCR efficiency of city and county governments is 0.951, a 5% operating improvement is available.