If tax rates are raised above a certain threshold, w hich is, however, impossible to determine precisely, the behavioural response of those w'ho have to bear the greatest share of the tax burden may cause the tax base to shrink along with the economic activity that determines the tax base. One recent study has found that current top income tax rates in most OECD countries are well below' those at which the total tax yield would be maximized (Piketty, Saez and Stantcheva, 2011). According to this study, revenue-maximizing top marginal income tax rates range between 57 per cent and 83 per cent.