. . . we may soon see a migration in the opposite direction: American baby boomers heading south of the border for their retirement years, seeking cheaper healthcare, more sun and more affordable living conditions.

There already are an estimated one million American retirees in Mexico, and hundreds of thousands more in Central and South America. While U.S. isolationists say undocumented migrants bloat hospital costs in the United States, their Latin American counterparts may soon say the same about U.S. retirees.

The reason for all of this is that Latin America's population is aging fast, and the region soon will have a much smaller pool of young people ready to work in the United States, Spain or other developed countries.

According to the United Nations Population Division, the number of Latin American and Caribbean people age 18 to 23 will drop from nearly 63 million nowadays to 59.6 million in 2050. Conversely, the number of people over 65 in the region will rise from 6.4 percent of the population nowadays to 18.4 percent in 2050.

"The United States always takes it for granted that people from all over the world want to move here. In 20 to 30 years, it may not be that easy to attract human capital to this country," says Phillip Longman, a demographer with the New American Foundation and author of The Empty Cradle: How falling birthrates threaten world prosperity.

In a telephone interview, Longman told me that countries like Spain, Germany and Japan will increasingly compete with the United States for new immigrants. "Immigrants will be a hot commodity," he said. . . .

Declining birth rates may allow most of Latin American countries -- with few exceptions, mostly in Central America -- to enjoy a few years of social peace before their populations grow old, and they have to take care of their elderly. In the short run, fewer children will mean the region will need to create relatively fewer jobs.

"In pure demographic terms, Latin America is poised to have a fairly prosperous period for about the next 30 years, which is another reason why fewer Latin Americans may need to migrate," said Longman. "You have this little sweet spot, where you have few children but not too many elders."