Tax-Timing Options and the Demand for Idiosyncratic Volatility
Investors have a choice over when to incur taxes on individual investments, and typically benefit from delaying the realization of capital gains while harvesting losses. This option implies that the effective tax rate on capital losses exceeds the one on capital gains, resulting in a convex after-tax payoff. Convexity creates a demand for idiosyncratic volatility (IVOL) within a well-diversified portfolio, and can therefore explain the puzzling negative relation between IVOL and expected stock returns. A simple model with tax-timing options predicts that the demand for idiosyncratic volatility increases with the tax rate, the nominal interest rate, and unrealized capital gains, and we show that all three measures predict the IVOL premium in the time-series. In the cross-section, we show that the magnitude of the IVOL premium increases with investors' average tax exposure.
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