The recent publication by Greece of the names of the most notorious tax cheat is the latest event in a recent trend by tax authorities across the world as they try to secure more revenue. Of course, it is difficult to evaluate how much underreported taxable income there is. One way, recently reported here, is to look at money circulation. A "natural experiment" can be much more illuminating.
Péter Elek, János Köllő, Balázs Reizer and Péter Szabó look at a recent reform in Hungary, wherein a minimum contribution to social security is imposed for any wage below twice the minimum wage. Firms paying below this threshold also face more scrutiny from tax authorities. One has to understand that one feature of wage under-reporting is that it can lead to a the declaration of an official wage at the minimum wage with the rest paid under the table. The Hungarian reform had the potential to change this for cheaters, who would then want to declare twice the minimum wage.
Using a double-hurdle model, because there is also a censoring problem with the minimum wage in additions to the tax cheating selection, the authors find that about 50% of the minimum wage job before the reform were fraudulent. With about a third of workers declaring a minimum wage, that is a considerable share of cheaters. And there may of course be more, who declare more than minimum.