Since 1996, the IMF has modified HIPC in several ways, often in response to the shortcomings its critics have highlighted. The IMF first restructured HIPC in 1999. These revisions modified HIPC's threshold requirements. Today, HIPC defines three minimum requirements for participation in the program. First, as before, a country must show its debt is unsustainable; however, the targets for determining sustainability decreased to a debt-to-export ratio of 150% and a debt-to-government-revenues ratio of 250%. Second, the country must be sufficiently poor to qualify for loans from the World Bank's International Development Association or the IMF's Poverty Reduction and Growth Facility (PRGF, the successor to ESAF), which provide long-term, interest-free loans to the world's poorest nations. Lastly, the country must establish a track record of reforms to help prevent future debt crises.