EVEN IN THE poorest regions of the world, standards of living are visibly rising. In the countries in the middle range of wealth, rates of progress are often spectacular. The World Bank has again published its annual description of the process, and its prospect for the rest of the century. The bank describes what you might call the long waves of history -- the slow trends of demography and development that are visible only in long perspective. This time it pays particular attention to the hundreds of millions of people who, over the next two decades, will be pouring into the gigantic cities of countries not yet fully industrialized.

Two decades ago, in the very poor countries of southern Asia and Africa, life expectancy for a newborn child was 42 years. Today it's 50. In the same period, among the middle range of countries running from Egypt at the least wealthy end of the scale up to Spain, life expectancy has risen from 53 years to 60. In the industrial world, it's up from 69 to 74 74. Wealth can buy a society a lot of things, and one of them is life itself. Another is literacy and access to education, which have been rising equally fast.

Birthrates have come down significantly, nearly everywhere, over these two decades, but not so fast as death rates. The world's population is now over 4 billion, and the World Bank estimates that it will go up to about 6 billion by the end of the century. In 1950, there were only six cities with more than 5 million people and all but one -- Buenos Aires -- were in the industrial world. By the end of the century, the bank estimates, there will be at least 30 cities that big and 18 of them will be in the developing world. One, Mexico City, may well reach 30 million. During the middle 1970s, both Mexico City and Sao Paulo were growing at a rate of half a million people every year.

In these vast cities, whose ideas or progress will prevail? For some of their citizens, transportation means clearing streets of vendors and pedestrians to enable their cars to move. For them, education means universities and health care means modern hospitals. But for most of the people in those cities, streeets will be useless without buses, and education means free elementary schools. For them, health depends less on clinical care than on the state of the water supply and the sewers. In some of these countries, although not for the world as a whole, food production per capita has recently been sliding downward. For most people on this earth, the terms of life and death will be set less by the doctors than by the farmers and the plumbers.

The World Bank, as you might have suspected, does not offer these forecasts merely for their academic interest. It wishes to remind you that the process of development works -- faster in some places than in others, but measurably almost everywhere. The bank also wishes to remind you why it works. For the developing economies, for example, it is crucial to be able to export their products into the markets of the rich industrial nations. It is also crucial to keep getting the development capital that those rich nations, like the United States, provide through channels like the World Bank.