Poor countries across Africa, Central America and the Caribbean are losing sometimes staggering portions of their college-educated workers to wealthy democracies, according to a World Bank study released yesterday.
The study's findings document a troubling pattern of "brain drain," the flight of skilled middle-class workers who could help lift their countries out of poverty, some analysts say. And while the exact effects are still little understood, there is a growing sense among economists that such migration plays a crucial role in a country's development.
The findings are based on an extensive survey of census and other data from the 30 countries in the Organization for Economic Cooperation and Development, which includes most of the world's richest nations.
The study found that from a quarter to almost half of the collegeeducated citizens of poor countries like Ghana, Mozambique, Kenya, Uganda and El Salvador lived abroad in an O.E.C.D. country - a fraction that rises to more than 80 percent for Haiti and Jamaica.
These patterns suggest that an extensive flight of educated people is damaging many small to medium-size poor countries, while the largest developing countries are better able to weather relatively smaller losses of talent, and even benefit from them when their skilled workers return or invest in their native lands, said Frédéric Docquier, a lead researcher for the bank and an economist at the University of Leuven in Belgium.
"For a country with a third of its graduates missing, one has to worry," said Alan Winters, director of the World Bank's development research group.
The World Bank study, published yesterdayin a book, "International Migration, Remittances and the Brain Drain," also presents an analysis of the effect of the money that migrants from Guatemala, Mexico and the Philippines sent home, typically to their families.
Those payments, known as remittances, helped reduce poverty in those countries and were a major source of foreign exchange, but the broader implications were complex.
In Guatemala, for example, rural families receiving the money spent more on education and less on consumption. But in Mexico, children in migrant families actually got less education than those of nonmigrants, possibly because their families believed that they would eventually migrate to the United States for unskilled jobs that did not reward higher levels of learning.
Some of the bank's data on brain drain have brought debate. Mark Rosenzweig, a Yale University economist, argues that the bank's measurement is inflated because it does not exclude immigrants who moved to a rich country as children, or who got their college educations there.
Survey data on immigrants from Jamaica, for example, show that almost 4 of 10 came to the United States before the age of 20, he said.
Bank researchers say they are now gathering such information, though it is not available for many countries, and acknowledge that it would be useful to know where migrants were educated. But they and some experts outside the bank say its latest report still offers the most comprehensive sense yet of the magnitude of the brain drain from poor countries, though that knowledge is admittedly rough and incomplete.
Most experts agree that the exodus of skilled workers from poor countries is a symptom of deep economic, social and political problems in their homelands and can prove particularly crippling in much needed professions in health care and education.
Jagdish Bhagwati, an economist at Columbia University who migrated from India in the late 1960's, said immigrants were often voting with their feet when they departed from countries that were badly run and economically dysfunctional. They get their government's attention by the act of leaving.
"If you stay you don't have any bargaining power at all," he said.
But some scholars are asking whether the brain drain may also fuel a vicious downward cycle of underdevelopment - and cost poor countries the feisty people with the spark and the ability to resist corruption and incompetent governance.
Devesh Kapur and John McHale argue in their book, "Give Us Your Best and Brightest," published last week by the Center for Global Development, a research group in Washington, that the loss of institution builders - hospital managers, university department heads and political reformers, among others - can help trap countries in poverty.
"It's not just the loss of professionals," said Mr. Kapur, an associate professor of government at the University of Texas at Austin. "It's also the loss of a middle class."
The question of what can be done to lessen the damage is vexing and gets into difficult questions of whether to limit the migration of skilled workers. The immigration policies of rich nations, including the United States, Canada, Britain and Australia, have sought to attract highly educated professionals, to bolster their competitiveness and to fill gaps in domestic skills.
Many experts say they oppose efforts to curtail the movement of migrants, but they are debating possible ways to help poor countries cope. An idea that Professor Bhagwati first proposed in the 1970's - that developing countries should tax their expatriate workers - is getting a fresh look.
Editors of the World Bank's book say policies may be needed to raise the incomes of professionals in their home countries.
Others, including Professor Kapur and Professor McHale, who is an economist at the business school of Queen's University in Kingston, Ontario, suggest that new ways be found to compensate the hardest-hit countries for their losses. They also say rich countries should consider setting up time-limited visas that would allow professionals to work for a few years before taking their expertise, and savings, back home.
Professor Kapur likened a skilled immigrant's getting a visa to work in a rich country to winning a lottery, because the income gains from moving are so great. Whatever the approach, he said, the benefits to the few who are lucky enough to leave need to be weighed against the costs to their countrymen left behind.