Estimating Tobin’s Q for Listed Firms in Korea (1980-2005): Comparing Alternative Approaches and an Experiment with Investment Functions

Tobin’s Q is the most common measurement of firm value and performance. However, estimating Tobin’s Q accurately is not easy. Researchers have used book values of debts or assets rather than the market values. We estimate Tobin’s Q for listed firms in Korea from 1980 to 2005 based on replacement costs of assets as well as market values of debts and common and preferred stocks. We com- pare the estimates using the modified annual average depreciation rates and economic depreciation rates. In sum, we present and compare four alternative series of Tobin’s Q measures. We then estimate investment functions with alternative Tobin’s Q values as regressors to compare the reliability of alternative estimates. We find that the simple measure of using book values of both debts and assets is the most unreliable.