In a second-best optimal growth setup with only factor taxes, it is in general optimal to fully replace capital by labor income taxation in the long run. We revisit this important issue by developing a human-capital-based endogenous growth model with frictional labor search, allowing each firm to create multiple vacancies and each worker to determine market participation. We find that the conventional efficient bargaining condition is necessary but not sufficient for achieving constrained social optimality. We then conduct tax incidence exercises in balanced growth by calibrating to the U.S. economy with a preexisting 20% flat tax on capital and labor income. Our quantitative results suggest that, due to a dominant channel via the interactions between vacancy creation and market participation, it is optimal to switch only partially from capital to labor taxation in a benchmark economy where human-capital formation depends on both physical and human-capital stocks. This main finding is robust even along the transition with time-varying factor tax rates. Moreover, our quantitative analysis under alternative setups suggests that while endogenous human capital and labor-market frictions are essential for obtaining a positive optimal capital tax, endogenous leisure, nonlinear human-capital accumulation and endogenous growth are not crucial.
Long-Run Tax Incidence in a Human Capital-based Endogenous Growth Model with Labor-Market Frictions