In empirical analysis, the Kakwani index is the most frequently used indicator for comparing progressivity across countries and over time. The Kakwani is often assumed to measure to what extent a policy design is targeted to the poor. It has, however, a major drawback: it is not defined for net...

The adverse distributional effects of a flat tax are well known and have been documented by empirical research in several countries, including Belgium. Advocates of the flat tax argue, correctly, that many of these studies do not take into account agents' behavioural reactions and possible feed...