臺灣的教育機會競爭激烈性與教育世代的出生規模有關嗎？其關係是否與教育制度變革有所關聯呢？為了回答這兩個研究問題，本研究探討臺灣1940-1992年間，同一年出生者（即同一個出生世代）在教育歷程中的教育機會競爭激烈性之變化，並分析出生世代規模對其不同教育進階的教育機會競爭激烈性之影響。同時，探究出生世代規模對其教育機會競爭激烈性的影響，如何因不同的教育制度變革而變化。分析資料為1940-1992年共53個單年出生世代的世代規模，以及其三個教育進階（國初中進階、高中進階和大專進階）的教育機會競爭激烈性和世代所經歷的教育制度變革等變項。以多層次成長曲線模型分析每個出生世代在不同教育進階的教育機會競爭激烈性。分析結果顯示：同時考慮世代規模與教育制度變革對教育機會競爭激烈性的影響時，世代規模對於國（初）中進階教育競爭激烈性為負向的影響，對於高中進階教育競爭激烈性沒有影響，然而，世代規模愈大，則其大專進階教育競爭激烈性愈高。另外，出生世代規模對其各教育進階教育機會競爭激烈性的影響效應，的確因出生世代所經歷的教育制度變革而有所不同。換言之，臺灣教育制度變革的確調節了出生世代規模，對於教育機會競爭激烈性的影響效應。

This paper explores the trend of educational opportunity competition at different educational levels over different birth cohorts, examines the effect of cohort size on the competition for educational opportunity at different educational level, and tests whether the effect of cohort size on competition for educational opportunity differs by educational reform stages. With data from Education Statistics of the Republic of China, 1958-2010, a multilevel growth curve analysis is employed to analyze the relationships between birth cohort size and competition for educational opportunity at different educational levels, and to assess whether its relationship changes across educational reform stages. The results reveal that birth cohort size has a negative effect on the competition for educational opportunity at the junior high school level, no significant effect at the senior high school level, and a positive effect at the college level when holding the effect of educational reform constant. Moreover, the effect of birth cohort size on the competition for educational opportunity differs by the stage for educational reform. In other words, educational reform does moderate the magnitude of the effect of cohort size on the competition for educational opportunity.