Monopolistic competition, rising markups, and optimal taxation of participation

This study explores the optimal taxation of participation within a monopolistically competitive product market that exhibits increasing markups. Individual labor supply responds along both intensive and extensive margins. The government simultaneously optimizes a nonlinear Mirrleesian income tax scheme, a flat profit tax rate, and a flat unemployment benefit. It is shown analytically that the monetized welfare cost of an increase in unemployment benefit is higher under monopolistic competition compared to under perfect competition. Nevertheless, numerical simulations suggest that the optimal unemployment benefit increases in response to greater markups when the government simultaneously optimizes all of its tools. The reason is that, along with a higher profit tax, rising markups require a decline in marginal income taxes. Lower marginal income taxes relieve the extensive margin distortions and accommodate an increase in the unemployment benefit. Accordingly, optimal nominal participation taxes remain approximately unchanged for the lower half of the ability distribution. For the upper half, the decline in income taxes outweighs the increase in the unemployment benefit, leading to lower optimal nominal participation taxes.