The purpose of this paper is to consider the problem of optimal income taxation in the domain of progressive (convex) income tax function. This paper proves the existence of an optimal tax function and that the optimal marginal and average tax rates tend asymptotically to 100 percent as income level becomes arbitrarily high.
Kaneko, Mamoru, "The Optimal Progressive Income Tax — The Existence and the Limit Tax Rates" (1981). Cowles Foundation Discussion Papers. 835.