Tax systems with separate taxation of wage and capital income, also called dual income tax systems, have gained relevance through the Mirrlees Review. Obviously, such tax systems are exposed to horizontal equity (HE) failures, or horizontal inequity (HI). HE and HI have a firm grip on assessment...

Inequality of post-tax income among pre-tax equals is evaluated andaggregated to form a global index of horizontal inequity in the income tax.The vertical action of the tax is captured by its inequality effect on averagebetween groups of pre-tax equals. Putting the two together,...