所得稅損失扣除政策有效率嗎？

Is the Income Tax Deduction Efficient ?

Kaplow (1991, 1992)在其著名的文章中指出所得稅損失扣除政策會扭曲投保人的保險決策因而導致效率的損失，然而弔詭的是實務上許多OECD國家都有類似政策。有鑑於此，後續許多文獻即嘗試從不同角度來合理化該種現象。不過，令人遺憾的是，既存文獻所提出的理由並不充分，我們認為政府承擔風險的能力較高，才是上述政策普遍存在的原因。文中我們建構一個模型來說明此一現象，並且導出損失扣除政策得以增進社會福祉的充分必要條件：若引進損失扣除政策得以降低社會的總合風險成本，則實施該政策可增進社會的福祉，反之，則會降低社會的福祉。

Assuming that insurers are risk neutrality, Kaplow (1991, 1992) shows that the income tax deduction will induce the insured to buy partial insurance, which in turn distort their insurance decision. Thus welfare with deductions will be lower than without deductions. Nevertheless, we can find that most OECD countries have implemented this policy. Although a few literature has continued to address the need for government intervention in the provision of income tax deductions, these literature still lack a rational reason for carrying out tax deductions. Therefore, the more likely explanation in implementing tax deductions is that the government has more risk-taking abilities than the insurer and insured.