所得不確定下的生育與年金制度

Fertility and Pension System under Income Uncertainty

王翊凱(Yi-Kai Wang)

指導教授 ： 江莉莉

淡江大學/商管學院/經濟學系碩士班/碩士(2015年)

https://doi.org/10.6846/TKU.2015.00675

摘要

近年來，超低生育率的現象在世界各國漫延開來。針對低生育現象，過去文獻提出的理由主要為女性勞參率、薪資與教育程度的提升。然而，這些因素在不少國家中已發展到一定階段，生育率依然持續下降，顯示現今可能存在新的因素影響著生育率。少子化現象通常伴隨著人口高齡化，此時老年人口的生活保障也是政府必須面對的問題，而年金制度便是最普遍的ㄧ項因應措施。
本文建立一個兼採利己與利他動機的疊代生育模型，並納入隨收隨付之年金給付，探討決定生育的因素，尤其著重於年金制度的實施對生育決策的影響。有鑑於現今社會普遍認為經濟發展前景不明朗，父母對子女未來的所得無法充分預期，故本研究除原本設立的充分預期下之生育模型外，又延伸發展成所得不確定的生育模型，重新求解最適生育的決策，並比較所得確定與不確定兩種情況下之結論差異。本文接續採用數值模擬的分析方法，給定未實施年金制度的起始狀態，分別模擬所得確定與不確定兩種情況下各項外生變數對父母的生育數以及儲蓄與遺產決策的影響。其後引進年金制度，進一步模擬實施年金制度下的決策變動，並與沒有年金制度的結果做交叉比較。
本研究發現生育減少的潛在原因包括：養育成本提高、父母財富減少、父母更加注重消費或遺產的贈予，以及預期子女所得下降。除此之外，本文認為造成生育率持續下降的新成因之一為在社會大眾預期未來悲觀下，因應未來高齡化社會所實施的年金制度。假使民眾認為未來經濟狀況差，對子女未來的所得預期悲觀，此時年金制度對於提升生育的效果有限；甚至如果父母預期子女所得十分低下時，年金制度施行將會使得目前生育率低落的現象雪上加霜。

關鍵字

生育 ； 年金制度 ； 所得不確定

並列摘要

Recently, the phenomenon of the extremely low fertility has spread all over the world. Most early research stressed that it was resulted from the increases of the labor participation rate, wage level and educational status of female population. These factors have now been relatively stable; yet, the total fertility rate still keeps declining in many countries. This implies that there must be new factors that underlie the recent fertility trend. The low fertility is always accompanied by the aging population. It follows a problem that governments are facing; that is – how to provide income support for the elderly. A pension system is one of the most important programs.
This study proposes a cross-generation fertility model, with both self-interest and altruistic motivations and a pay-as-you-go pension system, to investigate the determination of fertility, especially focusing on the influence of the enforcement of pensions. Given that the future of economic development is uncertain, parents can’t precisely predict their children’s income in adulthood. Hence, this study also extends the fertility model to an uncertain one to explore parents’ decision on fertility based on the beliefs about children’s future income and to compare the results with those obtained under certainty. Except the theoretical analysis, this study carries out numerical stimulations under various regimes. We first simulate a situation with no pensions, and observe how exogenous variables affect parents’ decisions on fertility, savings, and bequest, respectively. Then we introduce a pension system and make further comparisons.
This study finds the potential reasons of low fertility, including an increase in raising costs, a decrease of parents’ wealth, more emphasis on parents’ own consumption or the giving of bequest, and the pessimistic expectation on children’s income. Furthermore, this study asserts that the enforcement of pension programs is probably a new cause of the persistence of low fertility. While people believe the economy is going worse in the future and the prediction about their children’s income is pessimistic, the influence of pay-as-you-go pensions on fertility turns to be negative. If people predict their children’s income is extremely low, then the enforcement of pension programs will worsen the low fertility.

並列關鍵字

fertility ； pension system ； income uncertainty

參考文獻

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