租稅減讓或定額補貼－－實質選擇權之探究

Tax Credits or Lump-Sum Subsidies--The Real Option Approach

提昇廠商之投資意願為政府諸多政策目標中相當重要之一環，但政府如何能以較少之成本來達成政策目標亦不容忽視。然而，大部份之文獻致力於政府如何以政策改變廠商之投資誘因，主要以廠商的角度切入此議題。本研究則由政府的角度出發，分析在給定投資臨界值下，不同的鼓勵投資政策對政府之負擔有何差異，從而決定何種型式之政策較能收控制政策成本之效。本研究發現在給定投資臨界值下，三種政策中（定額補貼、降低邊際利潤稅率及免稅T 時期，再回復課稅）以定額補貼最有控制成本之效果。此外，亦發現在市場波動度愈大時，不同型式政策對投資臨界值影響之差異程度愈大。因此，波動度愈大，愈顯定額補貼控制政策成本之效。

To promote the investing incentives of firms is an important policy target for a government, no matter through tax credits or lump-sum subsidies. The early literature on investment ignores some crucial characteristics of an investment project, namely, irreversibility and uncertainty, which may in turn make it worthwhile for a firm to wait to invest in the project. Such features are the foundation of the real option approach. Moreover, most of the literature aims at how different forms of policies affect the incentives of firms to invest. Instead, this study analyzes the regarding issue from the point of view of a government by incorporating the neglected nature of an investment project. The real option approach is thus adopted. To be more precise, the focus here is to investigate which form of tax policies saves most for a government, given the critical value for firms to invest. It is assumed that one firm is able to exercise a new technology (i.e. a new project) which generates a permanent random cash flow. In order to do so, the firm has to incur costs of installing required equipments, which are irreversible. Three types of policies are examined to see which one saves most for a government, namely, lump-sum subsidies, lowering marginal profit tax rate, and tax holidays. We find that, given the critical value for firms to invest, lump-sum subsidies can save the government most among the alternative policies, while the other two give the same results to the government. In addition, how much lump-sum subsidies save increases in market volatility. The more volatile an industry, the more lump-sum subsidies save for a government.