 One of the early criticism that questioned the use of the terms "developing" and "underdeveloped" countries, was voiced in 1973 by prominent historian and academic Walter Rodney who compared the economic, social and political parameters between the United States and countries in Africa and Asia.There is "no established convention" for defining "developing country".According to economist and sustainable development expert Jeffrey Sachs, the current divide between the developed and developing world is largely a phenomenon of the 20th century.