ABSTRACT
Does the preferential tax treatment of debt vis-à-vis equity cause banks to increase their leverage? We compile a novel dataset that allows us to study the evolution of the tax advantage of debt in advanced economies from 1870 to 2017. Based on nearly the entirety of advanced-economy tax shield changes since the nineteenth century we show that a 1 percentage point increase (ppt) in the tax shield elicits state-dependent capital ratio responses in the -0.2 to -0.6 ppt range. This implies that the preferential tax treatment of debt was an important contributor to the increase in bank leverage over the twentieth century.