The amount of money paid worldwide in bribes is between 1.5 trillion and 2 trillion dollars, or about 2 per cent of the value of the world's economic output, the head of the International Monetary Fund (IMF) said Wednesday, according to dpa. Christine Lagarde quoted the figure from recent IMF research in an open letter published one day before the start of an anti-corruption summit in London. She said the amount is an estimate of the total value of bribes paid annually in both developing and developed countries. Lagarde wrote that corruption - defined as an abuse of public office for private gain - "undermines trust in government and erodes the ethical standards of private citizens." While the direct economic costs of corruption are well known, "the indirect costs may be even more substantial and debilitating, leading to low growth and greater income inequality," Lagarde wrote. British Prime Minister David Cameron is hosting the global Anti-Corruption Summit on Thursday, providing global leaders their first opportunity to meet in the wake of the anonymously leaked Panama Papers. Lagarde addressed the belief that corruption is primarily a cultural problem that takes generations to address, saying that there are examples of countries that have managed to make significant progress in addressing corruption in a relatively short time. Some developing countries have less of a problem with corruption than some developed countries, the IMF chief said. Lagarde also said in order to fight corruption, a multifaceted approach that promotes transparency and strong institutions centered on a professional civil service is needed.