心理因素與年金之謎

Abstract

在人們該如何確保未來老年的經濟生活安全的議題上，生存年金因能提供購買者長期而穩定的現金流量，被視為眾多金融商品中，用來規避長壽風險的最適工具。然而，在現實社會中，除了少部分強制年金外，商業年金的需求普遍偏低，因而形成所謂的「年金之謎」。相關文獻顯示，遺產動機、年金商品的價格、社會安全制度的排擠、家庭分散風險的能力等，都是造成年金之謎的可能原因。近年來，隨著心理因素與投資決策之相關研究的增加，許多學者也開始探討心理因素對人們購買年金商品的決策的可能影響。 本文分別為兩個部分，在兩期的預期效用模型架構下，探討兩種不同的心理因素對個人年金購買決策的影響。第一部分係參考Caplin and Leahy (2001)所建構的預期焦慮模型，分析人們的決策受到焦慮心理因素的影響時，其投資組合中，年金的比例是否會降低。此外，若人們會因為實際結果不如預期會產生失望的情緒反應時，其事前的決策行為也會不同。因此，第二部分則參考Laciana and Weber (2008)，在模型中加入失望情緒的心理因素，探討失望的可能程度對投資年金商品決策的影響。數值模擬結果顯示，當人們的消費決策行為受到心理因素的影響時，對年金的投資比例會明顯降低。因此，心理因素亦為造成年金之謎的可能原因。

The “annuity puzzle,” which describes the inconsistency between the theoretical prediction of full annuitization and the low rate of annuitization in reality has recently been widely discussed in the literature. Recently, literature has begun to take into consideration of individual’s psychological emotions to understand how anomalies in decision-making under risk may affect the annuity purchase decision. In Part I, we propose that anticipatory anxiety may be one of the rationales for the annuity puzzle. By setting up a two-period model under anticipatory anxiety, as modeled by Caplin and Leahy (2001), we find that the optimal conditions for partial annuitization as well as the optimal annuitization level are sensitive to the degree of anxiety. Moreover, given reasonable parameters, our simulation results show that anxiety can explain why individuals annuitize their income at a relatively low level. In Part II, we incorporate the disappointment effect into the two-period model and derive the optimal conditions for partial annuitization. Simulation results show that the optimal annuitization level is sensitive to the intensity of disappointment. Therefore, this paper presents another rationale for explaining why individuals annuitize their income at a relatively low level, even when guarantees are provided.