For the last 10 years, people in China have been sending me money. I also get money from countries in Latin America and sub-Saharan Africa — really, from every poor country. I’m not the only one who’s so lucky. Everyone in a wealthy nation has become the beneficiary of the generous subsidies that poorer countries bestow upon rich ones. Here in the United States, this welfare program in reverse allows our government to spend wildly without runaway inflation, keeps many American businesses afloat and even provides medical care in parts of the country where doctors are scarce.

Economic theory holds that money should flow downhill. The North, as rich countries are informally known, should want to sink its capital into the South — the developing world, which some statisticians define as all countries but the 29 wealthiest. According to this model, money both does well and does good: investors get a higher return than they could get in their own mature economies, and poor countries get the capital they need to get richer. Increasing the transfer of capital from rich nations to poorer ones is often listed as one justification for economic globalization.

Historically, the global balance sheet has favored poor countries. But with the advent of globalized markets, capital began to move in the other direction, and the South now exports capital to the North, at a skyrocketing rate. According to the United Nations, in 2006 the net transfer of capital from poorer countries to rich ones was $784 billion, up from $229 billion in 2002. (In 1997, the balance was even.) Even the poorest countries, like those in sub-Saharan Africa, are now money exporters.

How did this great reversal take place? Why did globalization begin to redistribute wealth upward? The answer, in large part, has to do with global finance. All countries hold hard-currency reserves to cover their foreign debts or to use in case of a natural or a financial disaster. For the past 50 years, rich countries have steadily held reserves equivalent to about three months’ worth of their total imports. As money circulates more and more quickly in a globalized economy, however, many countries have felt the need to add to their reserves, mainly to head off investor panic, which can strike even well-managed economies. Since 1990, the world’s nonrich nations have increased their reserves, on average, from around three months’ worth of imports to more than eight months’ worth — or the equivalent of about 30 percent of their G.D.P. China and other countries maintain those reserves mainly in the form of supersecure U.S. Treasury bills; whenever they buy T-bills, they are in effect lending the United States money. This allows the U.S. to keep interest rates low and Washington to run up huge deficits with no apparent penalty.