Marginal tax rate & dynamics
I agree with the basic idea about the disincentive effects of marginal tax rates. Namely, economic theory assumes maximising agents, and the condition for a maximum can normally be expressed in terms of marginals. However, the marginal must be computed correctly. Above marginal rate r is only a static rate, that applies to a specific regime, for example a specific period. However, tax rates are adjusted from year to year. A dynamic situation requires a dynamic analysis.
Let
y = y - y[-1]. Then the proper (dynamic) marginal tax rate is DMR =
T /