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　　Since the mid 1950s, life expectancy around the world has increased greatly, and many scientists believe that this trend (趋势) is likely to continue in the future.

　　 The United Nations figured that in the early 1950s the world life expectancy rate was 46.4 years. By 1998, world life expectancy had increased to 63 years. In more developed regions, life expectancy was an average of 75 and in less developed areas it was 62 years.

　　The main reason for the increase during this period was the decrease in infant mortality (婴儿死亡率). This was mainly because of improved healthcare and better food production.

　　Most experts believe that people will continue to live longer in the future because of medical advances. Researchers predict that at least half of the North American and Japanese babies born since the year 2000 will live to an age of 90. Besides, new drugs are being developed which will slow down the ageing process.

　　If the present older populations in many countries become healthier, wealthier and live longer, the trend will have important results for people and governments. The cost of medical care for older people will rise, and governments will have to start thinking hard about how to provide money for state pensions(养老金) for older citizens. Some people will want to keep on working later in their life, which could lead to changes in the age of retirement (退休). Others would prefer to retire early to enjoy having more time for themselves. This will create business opportunities for companies in the leisure (休闲) and entertainment industries and open up new sections of the market.

Finally, the effect on the world population will be great. Europe's population has been on the decrease for several years now as people prefer to have fewer children and families tend to be smaller. However, the population won't decrease as fast once these anti­ageing drugs start to become widely available. It's believed that the populations in China and India could rise by 500 million. An expert on population, Professor Shripad Tuljapurkar, says that "We could expect to see the world's