企業退休金計畫依給付方式之不同，可分為確定給付制（Defined Benefit Plans）與確定提撥制（Defined Contribution Plans）。這兩種退休金計畫在承擔退休所得的風險上各有優劣不同。過去的二十年中，許多研究發現美國有越來越多的公司採用確定提撥制的退休金制度。雖然，絕大多數研究同意這樣的趨勢，但對於此趨勢的成因卻始終沒有定論。本研究蒐集12年豐富的實證資料，建構一組追蹤資料 (panel data)，依主要計畫(primary plan)及補助性計畫(supplementary secondary plan)兩個層面，詳細追蹤每一年間企業雇主對退休金計畫選擇的變化，並利用多重羅吉斯動態回歸模型 ( dynamic multinomial logit model) 分析影響企業雇主在退休金計畫動態選擇改變的重要因素及各類型退休金計畫彼此間的互補與替代關係。

By using rich twelve-year panel data of long-standing firms, identifying the 401(k) plan as a distinct pension choice, and separating employers’ pension decisions at both the primary plan and the secondary plan levels, we provide new evidence about how long-standing firms change their pension choices during recent pension trend. The unique formulation of the proposed multinomial logit model with random-effects enables us to analyze the dynamic effects of industrial classification, plan age, firm size, and union status on employers’ pension choices. The estimation of the random-effects allows us to establish the general patterns in employers’ pension plan decisions that are independent of the time and plan characteristics. One striking empirical finding is that firms in the manufacturing industry are more inclined to switch their primary plans from defined benefit to defined contribution plans, including 401(k) plans.