Experts say young people in developing nations now enjoy a more gradual transition from childhood to adulthood, as compared to young people 20 years ago. Study released Wednesday explains why growing up is taking longer and what that means for education and marriage.

They are in better health, going to school longer and marrying later.

That is a snapshot of the roughly 1.5 billion young people ages 10 to 24 growing up in developing nations, as compared to the same group 20 years ago.

In the report "Growing Up Global," the National Research Council and the Institute of Medicine in Washington find that education is now a key factor in the transition from childhood to adulthood.

"There has been a very dramatic and historically unprecedented growth in school participation around the world, even in countries where the economic situation is not so good," said Cynthia B. Lloyd, research panel member and director of social science research at The Population Council.

She says educated youth are healthier, in part because students are less likely to engage in pre-marital sex than their non-enrolled peers. And she explains schooling and delayed marriage go hand-in-hand, especially when girls are educated.

"It isn't just that they get out of school later and therefor marry later," she said. "It is because of what they learn in school, the opportunities that schooling brings for them, the possibility that they may have a chance to work or have a job before they get married, so there are a lot of other things that go along with it."

She adds that educated girls have different expectations in terms of what they want in a husband and how many children they want to have, both of which affect the timing of marriage.

But the study found that almost 40 percent of young people in developing nations are marrying before their 18th birthday, the age of adulthood as defined by the United Nations.

"This is down from, I think, 52 percent 20 years ago, so there's notable progress," Ms. Lloyd said. "But from a human rights perspective, there is a lot of concern about the number of young people marrying before they complete their childhood."

While the research discusses growing up in developing nations throughout the world, Ms. Lloyd says the findings are particularly indicative of life for young people in India and China.

"Forty two percent of all of the young people growing up in the developing world live in two countries, India and China, and these two countries have been extremely dynamic in recent years in terms of their economies, opening up all kinds of new opportunities for young people in terms of the job market," she said.

Conversely, the study finds that adolescents in Sub-Saharan Africa face exceptional difficulties growing up because of HIV/AIDS and the region's poor economy.

Overall, the study says 325 million young people in developing countries are forced to live on less than $1 per day.

Ms. Lloyd says she hopes this research will help policy makers as they develop plans to reach the U.N. Millennium Development Goals, including the elimination of extreme poverty and the attainment of universal schooling.

The report concludes that policy makers must focus more attention and resources on young people, in part by providing better schools and higher education so young people can compete for jobs brought about by globalization.