最適保險契約與稅賦抵減

The Optimal Insurance Contract with Tax Deductions

本論文主要目的為檢視稅賦抵減對最適保險契約之影響。本文發現當政府對被保險人的淨損失提供固定比例稅賦抵減時，最適保險契約包含自負額以及共保，且當保險公司的變動成本為零時，最適自負額仍然不為零。若被保險人的絕對風險趨避指數為常數或遞減函數，邊際稅賦抵減比率的上升會使得最適自付額上升，換言之，所得稅賦抵減制度相當於政府提供額外的社會保險，因而縮減私人保險的最適承保範圍。此外，當保險公司為風險中立者時，最適邊際理賠並不受到政府實施稅賦抵減制度的影響。換言之，保險公司與被保險人之間的共保比例仍然維持不變。

We examine the impact of tax deductions on optimal insurance contracts. We find that, under a proportional tax deduction system, a nonzero deductible is obtained even though there are no variable costs for the insurer. On the other hand, the optimal coinsurance rate would remain at unity, even under the tax deduction system, when the insurer is risk neutral. A policy with an upper limit cannot be the optimal contract, no matter what tax deductions are provided for losses. Furthermore, unlike Kaplow’s (1992) finding that tax deductions reduce an individual’s demand for coinsurance, our results show that the implementation of tax deductions increases the deductible but may or may not decrease the coinsurance.