The simple division of the world into developed and developing countries is sometimes useful for analytical purposes. Many development models apply across a wide range of developing country income levels. However, the wide income range of the latter serves as an early warning for us not to overgeneralize. Indeed, the economic differences between low-income countries in sub- Saharan Africa and South Asia and upper-middle-income countries in East Asia and Latin America can be even more profound than those between high- income OECD and upper-middle-income developing countries.