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第五章 結論與建議
本研究提出多因子避險模型，讓壽險公司可以調整其所持有的商品組合的單 位數，配合避險資產的購買或放空，來規避長壽風險和財務風險所帶來的威脅，
達到自然避險的效果，且由於本研究所提出之避險模型可包含數種商品在內，亦 可解決 Wang et al. (2010)限制商品種類的問題。同時為因應人口老化的趨勢，壽 險公司近來積極開發各式訴求滿足老年人口退休需求的壽險商品，其中反向房屋 抵押貸款具有契約有效期間無須償還貸款之本金和利息、無追索權
(Non-Recourse)和放款形式具彈性等特性外，最吸引退休人口的是反向房屋抵押 貸款商品提供他們一個可以將流動性較差的房屋價值轉換為現金，減少“House rich and cash poor”的現象，讓老年人得以有足夠的現金支付其日常所需之開銷，
且不需搬離其原住所。
本研究根據數值分析結果可以獲得以下結論：
1、在假設其他條件不變，僅討論死亡率波動的情況下(如表 4)，可以發現包含 反向房屋抵押貸款商品的商品組合，其商品價值的波動會比不含反向房屋抵 押貸款商品的商品組合來的小，顯示含有反向房屋抵押貸款商品的商品組合 對於未來可能發生的長壽風險具有較佳的避險效果。
2、從表 4 的 Case2 和 Case3 的結果中發現，商品組合內包含的保險商品的保障 期間越短，商品組合價值受到死亡率和利率波動的影響就會越小。
3、在同時考慮死亡率風險和利率風險的情況下(如表 5)，所獲得之結果與表 4 一致，含有反向房屋抵押貸款商品之商品組合具有較佳的避險效果，且保險 商品的保障年限越短，避險效果越佳。
4、給定不同的可貸成數(如表 6)，對商品組合價值的波動影響不大，但對貸款 人而言，過高或過低的可貸成數均會帶來其他不良的影響，因此壽險公司在
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擔任反向房屋抵押貸款商品的借款人角色時，仍須審慎評估借款人與標的房 屋的各項條件，給予適當的貸款資金。
雖然發行反向房屋抵押貸款可能讓壽險公司遭受其他財務風險因子的影響，
但就近來越來越受關注的長壽風險(Longevity Risk)來說，包含反向房屋抵押貸 款商品的商品組合，其對長壽風險的避險效果會比傳統的年金壽險來的好，此現 象在本研究所假設的各種利率情境中都可以觀察的到。因此台灣壽險公司在未來 可嘗試銷售反向房屋抵押貸款這類商品，可以增加壽險公司的經營範圍，也可以 藉此抵銷人口老化所帶來的長壽風險威脅。
本研究仍可再從下述幾個方向做進一步的研究：1、本研究只滿足多因子避 險模型的一階條件，因此當死亡率或利率的變動幅度較大時，所能達到的避險效 果就會變差，若能滿足模型的二階條件，其所能適用的範圍將更廣泛；2、雖然 目前市場上已有將反向房屋抵押貸款債權證券化的商品，但因其計價模型較為複 雜，且與房屋價格的連動性並不一定明顯，因此在本研究中僅就利率風險這項財 務風險因子來做討論，後續研究可再針對反向房屋抵押貸款商品所存在房屋價格 風險來做探討，若能找到相對應的商品或是避險資產，則對於壽險公司將來發行 反向房屋抵押貸款商品將會有很大的助益；3、一般計算壽險和年金保險保費時，
兩者採用的死亡率是不一樣的，年金保險是使用年金生命表與壽險的生命表不同，
因此有可能會產生基差風險(Basis Risk)，但本研究因受限於樣本資料，僅能對 壽險和年金保險使用相同的生命表來計算其負債價值，各家壽險公司將來可以公 司內部的死亡率經驗，依照本研究所提出之多因子避險模型進行相關的避險工 作;4、本研究在進行商品組合分析時，並未考量資產與負債的平衡，因此會有商 品組合價值為負值的不合理情況發生，未來研究可先就資產負債平衡的觀點著手，
讓數值結果得以更符合現實情況。
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