By VOAI'm Barbara Klein.And I'm Christopher Cruise with EXPLORATIONS in VOA Special English. The number of young people in Africa is growing. So is the number of older people in Asia. In fact, the United Nations says that, very soon, every fifth person in the world will be over the age of sixty.This week, we tell how some areas are dealing with changing populations.How should countries prepare for the world's aging population? A United Nations report is urging countries to answer that question.Japan has the world's oldest population. Thirty percent of Japanese are older adults. The UN report says by the middle of this century, sixty-four countries will have that level of the population over age sixty.Jose Miguel Guzman is head of the UN's Population and Development Branch. He says people are living longer for many reasons. They include improved nutrition, medical developments, better health care, education and economic well-being. But he says the fact that more people are living longer can create problems."Steep population aging also means an increased demand for income security, health and long-term care, which creates huge socio-economic and cultural challenges that will need to be addressed with a strong political and appropriate social policy."The UN report says populations are aging in all parts of the world. The most-rapid age increases are in developing countries. In those countries, people live -- on average -- sixty-eight years. By twenty-fifty, the average person will live seventy-four years. Life expectancy is seventy-eight in developed countries. Children born today in developed countries can expect to live until the age of eighty-three.Richard Blewett is chief executive officer of HelpAge International, a publication partner of the UN report. He says, in many countries, older people are not seen as helping the economy."Governments are not really living up to the expectations of their senior citizens and they could do a better job. What's needed there is long term vision and strong political will and a clear sense of priorities."Mr. Blewett says sixty-seven percent of the older people who answered questions for the report said their biggest problem was employment discrimination. But he said some countries are beginning to see the advantages, or gains, of having older adults. For example, grandparents in rural China increasingly care for grandchildren as their parents move to cities to find jobs.Martha Farnsworth Riche is the former head of the United States Census Bureau. She says a community in Australia talked with its retirees about their transportation needs."One very simple thing that came up, was that people needed more time, pedestrians needed more time, to cross the street. Now there was (a suggestion to) run the street lights with longer green light time."Other changes include reforming social security systems in developed countries. Another is creating social safety systems in developing nations where traditional family support systems are disappearing. The report says the most cost-effective and humane thing a society can do for its older citizens is to invest in their health so they can remain active.Researchers are warning that aging populations present challenges for governments when economic productivity is falling. This year, the government in Singapore released a song dealing with a population issue. It urges young people to produce more children to help end a drop in fertility rates.The song is fun, but the problem is serious. By twenty-thirty, the number of older adults in Singapore will rise two hundred percent from current levels.The government is offering to pay up to three thousand two hundred fifty dollars for each of the first two children. It will pay almost five thousand dollars for the third and fourth children.Starting in the nineteen eighties, Asia's young, working-age population helped the area become an economic success. But things are changing. Donghyun Park is an economist with the Asian Development Bank. He says what is happening in Singapore is also happening in other countries."That the share of the elderly -- those aged sixty-five plus in total population -- as well as relative to the working age population is steadily increasing across, across developing Asia. And of course, I mean Asia's no different from the advanced economies, right, that experienced its demographic transition much earlier."Two years ago, more than twenty two percent of Japan's population was age sixty-five years or older. In recent weeks, Japanese political leaders have been asked how they plan to care for the growing number of older adults.In Thailand, the population older than sixty-five rose to just over seven percent in twenty-ten from three point six percent in nineteen seventy-five. Thailand's family planning efforts have led to much-smaller families. In the nineteen sixties, mothers had an average of five to six children. Now, that number has fallen to one point five. That is well below the number of births needed to keep the population count unchanged.Vipan Prachuabmoh is dean of population studies at Chulalongkorn University. She says the falling population threatens to have a long term effect."We concerned that we will have decline in the number of population in the labor force age -- right, so, so the numbers starting to decline. And we also see that we have very sharp rising in term of number and proportion of population in the old age group. So now we start to concern about the sustainability, development of the country because we still have problem in term of, we have, in term of human capital."The problem for governments is that increasing population growth to help keep productivity levels high can also create problems. Vipan Prachuabmoh says those issues include reforming the education system, increasing labor skills and preparing a new generation for an aging society.China and India have used family planning programs to help reduce population growth. But researchers say such efforts will have harmful, long-term effects.Parents choosing the sex of their children, and medical technology, have created large gender gaps. The UN Population Fund says there are one hundred seventeen million women "missing," mostly in China and India. The Fund has predicted that, by twenty-thirty, China and India will have fifty percent more men than women of marriageable age.Wolfgang Lutz is with the Wittgenstein Center in Vienna, Austria. He says worldwide, progress has been made in balancing population growth with fertility rates. But he says other issues remain. "It really depends on adding what some people call the quality dimension in addition to the quantity -- meaning, the focus on human capital, on education and health rather than just the head count. Lot of countries have made a lot of progress and it's also when you are sort of re-evaluating the global evidence and the, the drivers behind these recent declines in fertility and increases in economic well-being, health status. It is really the, the educational efforts -- particularly the education of girls -- has been one of the driving factors."The Asian Development Bank says education will help to solve the problem of an aging workforce. Better-educated and better-trained work forces can increase productivity, which leads to stronger economic growth.The World Bank says a lack of good jobs for an increasing number of young people in Africa threatens the continent's recent economic growth. The Bank says economic development is important to success, especially in areas south of the Sahara Desert.Shanta Devarajan is the World Bank's Chief Economist for Africa. He says the number of young people entering the work force is one of the main reasons Africa's economic growth will continue."Africa may be the only source of young people very soon, because the rest of the world is aging and some of the world -- including Europe and, and Japan and the U.S. -- are aging quite rapidly. So this is potentially -- Africa could be a great powerhouse in the future."Shanta Devarajan says a growing population of young people could threaten economic development if it is not controlled in the right way. "The most important risk or the most important threat is the fact that despite all of this growth, the number of productive jobs being created as a result of growth is still very limited relative to the number of young people entering the labor force every year."The World Bank says sales of natural resources can help developing countries, but they must be used to help improve the lives of average citizens. And good governance will help ensure that citizens, both rich and poor, can profit from such sales. Punam Chuhan-Pole is the World Bank's Lead Economist for Africa."If you look at the share of income that is going to the poorest twenty percent of the population, it is rather low. It's about six percent, which is comparable to what you see in other countries. So looking at, at how growth in these countries as well as wealth is impacting the poor, the results don't seem that promising."