Almost unknown in 1960, the value added tax (VAT) is now found in more than 130 countries, raises\ud around 20 percent of the world’s tax revenue, and has been the centerpiece of tax reform in many developing\ud countries. This paper explores the causes and consequences of the remarkable rise of the VAT. A key\ud question is whether it has indeed proved, as its proponents claim, an especially effective form of taxation. To\ud address this, it is first shown that a tax innovation—such as the introduction of a VAT—reduces the\ud marginal cost of public funds if and only if it also leads an optimizing government to increase the tax ratio.\ud This observation leads to the estimation, on a panel of 143 countries for 25 years, of a system of equations\ud describing both the probability of VAT adoption and the revenue impact of the VAT. The results point to a\ud rich set of determinants of VAT adoption, this being more likely, for example, if a country has a program\ud with the IMF and the less open it is to international trade. In the revenue equation, the presence of a VAT\ud does indeed have a significant impact, but also a complex one, with a negative intercept effect counteracted\ud by positive effects that are greater the higher are per capita income and, more tentatively, openness. While\ud the sign of the revenue impact of the VAT is thus in general ambiguous, most countries that have adopted a\ud VAT seem to have gained a more effective tax instrument in doing so (though this is less apparent in sub-\ud Saharan Africa), and most without it seem likely to gain from its adoption.