This paper attempts to provide a unified analysis of the effects of taxation on the equilibrium value of marginal q under alternative financial policies. It is shown that the q approach does not avoid all the specification problems associated with analyses based on the cost of capital. The (theoretically and empirically) crucial relationship between average and marginal q is also examined, and it is shown that, under UK and US tax rules, the possibility of winding up precludes persistent undervaluation in equilibrium.

The paper examines the effect of investment frictions on leverage dynamics, using a model of a firm whose investment projects are (1) indivisible and lumpy, and (2) subject to time-to-build. Regressions on the model-simulated data demonstrate that investment frictions can provide alternative interpretations of the observed leverages shown in the empirical literature. Cross-sectional analysis of firms in the oil and gas extraction industries, as well as analysis across all industries, reveals the evidence that small firms have more volatile investments and longer time-to-build, which may explain the observed differences in leverage dynamics across small and large firms.