Wealthy nations and international organizations, including the World Bank, spend more than $55 billion annually to better the lot of the world's 2.7 billion poor people. Yet they have scant evidence that the myriad projects they finance have made any real difference, many economists say, reports The New York Times. That important fact has left some critics of the World Bank, the largest financier of antipoverty programs in developing countries, dissatisfied, and they have begun throwing down an essential challenge.