本研究透過我國「家庭收支調查」及相關社會、經濟指標，探討我國中層階級流失現象及其成因，並提出社會政策的因應方向。主要研究發現為：（1）不論就家戶比率或可支配所得份額來看，自1980 年來我國確實出現中層階級流失的現象；2000-2005 年間尤其明顯。（2）1980-2005 年間，中、下層階級的平均經濟福利持續變差，僅上層階級的經濟福利提升。薪資結構兩極化及失業率上升是造成此現象的主因。政策建議有兩點，首先，我國社會救助制度有必要將近貧家戶納入保障範圍。再者，政府應建構更積極的社會保障制度，如薪資稅額扣扺制度、長期照顧制度與幼兒照顧。

This paper aims to examine the shrinking middle class and possible causes of this problem in Taiwan. The empirical analysis of this study is based on annual household income survey and socioeconomic indicators such as unemployment rate and effective tax rate. Major findings of this study are as follows: 1. Whether looking at changes in size or household disposable income share, the results did indicate that middle class in Taiwan apparently declined, especially during the period 2000-2005. 2. Average economic well-beings of middle class and underclass are getting worse, while that of upper class is becoming better. The reasons for such difference might be polarization of wage structure and rising unemployment rate. This study suggests that social assistance in Taiwan should cover the near-poverty groups. Besides, the government need to construct more active social security system such as earned income tax credit, long-term care and child care system.