ETHIOPIA REMAINS the world's poorest country. That's not astonishing, given the harsh land, the incompetent Marxist government and the entrenched civil war. Its GNP per capita runs about $110 a year, compared with $18,250 currently in this country. The next-poorest country is Bangladesh, which is better governed but desperately overpopulated.

The rankings come from the World Bank, which does annual estimates of GNP and other illuminating numbers for most of the world's countries. Its purpose is not merely to suggest the disparity between richest and poorest, which is pretty obvious, but to provide some reliable sense of the enormous variety of conditions in between -- and the rate at which things are changing.

At precisely the midpoint of the list stands Jamaica, with half the countries richer than it and half poorer. Living very close to the United States and the inescapable comparisons, Jamaica thinks of itself as poor. But it is, in fact, middle class. Life expectancy, a good measure of living conditions in general, is 73 years there -- far longer than in any but three or four other Third World countries and very close to the average expectancy of 76 years in the wealthy industrial democracies. Part of the explanation is Jamaica's school system, and most of its children of high school age are actually in school. Thanks to this high degree of literacy Jamaicans have more in common with Americans, in every respect but income, than the unfortunate people of Ethiopia or Bangladesh have in common with them.

Other countries clustered around the median on the World Bank's list are Botswana, Paraguay, Peru and Turkey -- a very mixed group. Botswana is one of the great successes of development economics. At independence, 21 years ago, it had one of the lowest incomes in the world -- as most of the black African countries still have. Today, despite drought and a vulnerable location on South Africa's border, it is halfway up the World Bank's income ladder. In contrast Paraguay stagnates under the rule of Gen. Alfredo Stroessner, its president for the past 37 years. Peru, deeply divided by race, geography and social class, devotes itself to a kind of populist politics that has proved to be death to economic growth. Turkey, on the other hand, is growing steadily under a model plan for dealing with foreign debts and inflation. None of these middle-class countries is rich, but none -- by the standards of the planet as a whole -- can be called poor.

The World Bank has argued for years that to divide the world into two zones, the developed and the underdeveloped, is misleading as well as patronizing. The gradations are infinite, and there are no longer clearly defined lines among the categorie