再探臺灣階級與世代的收入差異，1990-2020

REVISITING INCOME DIFFERENCES BETWEEN COHORTS AND SOCIAL CLASSES IN TAIWAN: 1990-2020

臺灣社會輿論關注貧富差距，特別是不同世代之間的所得差異與「世代正義」議題。然而，所得世代差異同時混雜了整體經濟循環及勞動者生命階段、以及其教育程度與社會階級等因素的影響，其中有時間因素的多重效果即人口學關注的「年齡（age）、時期（period）與世代（cohort）」（簡稱APC）效果。由於長期追蹤資料較多屬單一或少數世代的限制，在研究方法上，本研究希望以多次調查的橫斷面資料整併之後，運用APC的概念拆解所得的世代差異。本研究整合了多期橫斷面的家庭收支調查家內之個人所得，時間為1990-2020，並以APC內部估計模型同時呈現年齡、時期與世代的拆解效果，主要發現臺灣社會個人所得差異的變化趨勢如下：（1）個人所得的教育與階級差異擴大：雖然大學畢業生的平均收入下降、研究所以上的收入仍有提升；資本家與自營作業者、技術工人與非技術工人之間的差異隨著時間擴大，以及（2）戰後嬰兒潮與千禧世代之間收入差異持續顯著未見縮減。在結論與討論有改善調查方法的實務建議。

Income inequality, especially the generational gap of income and ＂generational justice＂ has become a hot topic for the public in Taiwan. However, the determinants of income variety among cohorts are a mixture of economic cycle, life course, education, social class, etc. The mixture also includes multiple factors about time, that is, the age-period-cohort (APC) effects in demographic studies. Many longitudinal surveys are unable to investigate the generational gap because the interviewees are limited in the same birth cohort. By applying the APC model to long-term datasets pooled from different waves of surveys, we estimate the trends of income from different cohorts, age groups and periods in Taiwan. Second, we pooled the Survey of Family Income and Expenditure to estimate the generational difference of personal income between 1990 and 2020 in Taiwan. The empirical evidence demonstrated the same patterns of personal income differences: (1) in contrast with increasing return of graduate school, the income return of university is shrinking; meanwhile, the income differences among employers, the self-employed, skilled workers (new middle classes), and unskilled workers has been amplified in the past three decades. (2) the income gap between the baby boomers and millennials has continued and implies a persistent generational inequality. Finally, each survey has its own advantages and limitations due to the questionnaires and research designs.