由於繳納保費等問題，台灣目前仍有不少人沒加入全民健保，本研究目的在探討個人的納保決策機制及影響其決策的個體及總體社會經濟要素。研究方法係以承保資料檔及人力運用調查連結檔案爲基礎，運用離散選擇理論建構未納保模型，控制個人基本特質和社會經濟屬性及總體社會經濟環境變數，藉以研究影響納保的要素。主要發現：(1)失業者的未納保率遠高於就業者，而非勞動力加入全民健保情形則有很大變異；(2)邊際勞工（主要包括勞力低度運用者、被迫離職者、採礦工、營建工、體力工、及其他非技術工等基層人員）相較其他勞動力較易被排除在健保體系之外；(3)總體社會經濟環境對個人是否加入健保有顯著影響，其中以經濟成長率、就業成長率、失業率、及醫療補助占縣市政府預算決算比率影響效果最爲顯著。研究主要結論是邊際勞工及年輕的就業人口中，有相當高的比例沒有全民健保且不受政策的重視，並且他們在社經體制中又屬於受剝奪的群體，因此是政策未來值得特別留意及加強的對象。

In light of the problem associated with the availability of medical care, this research aims to ascertain the determinants of socioeconomic inequalities affecting individual enrolment decision of the NHI program. Based on the data constructed by linking Manpower Utilization Surveys and the administrative records of National Health Insurance, the research utilizes discrete choice theory to construct the uninsured model, with crucial individual characteristics and socioeconomic status and aggregate socioeconomic ecological variables being controlled. Main findings are as follows: (1) for the labor force, the uninsured rate for the unemployed is four time as much high as that associated with the employed, while the disabled and elderly have the highest uninsured rate for those not in the labor force; (2) marginal laborers, including underutilized workers, those experienced involuntary turnover, miners, construction workers, production workers, and low-skilled laborers, are more prone to be uninsured than the ordinary people; (3) aggregate socioeconomic conditions like economic growth, employment growth, unemployment rate, and medical subsidy are crucial in accounting for the uninsured problem. Research findings suggest that marginal labor and the young are associated with substantially high uninsured likelihood that has long been much ignored by past policy. Because they are voluminous, relevant policy should pay more attention to these socially and economically deprived subgroups.