and thus, as noted above, the simplifications to the government's revenue collection apparatus might be offset by new government ministries required to administer those policies. Revenues Russia is considered a prime case of the success of a flat tax; the real revenues from its personal income tax rose by 25.2% in the first year after the country introduced a flat tax in 2001, followed by a 24.6% increase in the second year, and a 15.2% increase in the third year. The Russian example is often used as proof of the validity of this analysis, despite an International Monetary Fund study in 2006 which found that there was no sign "of Laffer-type behavioral responses generating revenue increases from the tax cut elements of these reforms" in Russia or in other countries. In 2021, Russia ended its flat tax on personal income as it introduced a second higher tax rate. Bulgaria's entry into the EU in 2007 was marked by a spur of reforms aimed at reducing the large share of informal economic activity, estimated at 43% in 2006. Parliament approved the introduction of a 10% corporate income tax rate for 2007, to be followed by a 10% personal income tax rate the next year. The IMF was wary of this reform, arguing that the simplified tax system would lower the budget surplus and encourage a larger current account deficit. At the time of these discussions, however, the Bulgarian government did not need external financing and proceeded with its reform plans. The year 2007 brought a huge growth of revenue from corporate income tax (by 39% compared with the previous year) and surpassed the Ministry of Finance's own forecast (27% year on year). The budget surplus rose despite considerable emergency spending at the end of the year. There were several reasons for this beneficial effect: (i) the tax rate limited the incentives for tax evasion, (ii) the optimism at the beginning of the country's EU membership, (iii) and the increase in foreign direct investment, which reached an all-time annual record of €9 billion (about 11% of GDP). Overall structure Taxes other than the income tax (for example, taxes on sales and payrolls) tend to be regressive. Under such a structure, those with lower incomes tend to pay a higher proportion of their income in total taxes than the affluent do. The fraction of household income that is a return to capital (dividends,