Hong Kong's population structure is changing faster than almost anywhere else in the world. It took a century for France's senior population to double, but that has almost happened here in just 25 years. In 1981, only 6 per cent of people in this city were aged 60 or above, but that number hit 11 per cent last year. There are three components in the study of population: deaths, births and migration. Deaths are not a particularly exciting issue because people will die anyway, and the number of deaths is stable. Migration is a more interesting subject. The city saw a lot of people leaving in the 1980s because of the impending political transition back to Chinese control. The government thought the situation would continue in the 1990s but, as it happened, many people returned from overseas. Officials did anticipate a drop in Hong Kong's birth rate, but they didn't expect it to decline so much. Our fertility rate is now 0.966 children per woman - one of the lowest in the world. The figure is even lower, at about 0.7, if we exclude babies born to visiting mothers from the mainland. If nothing is done, the birth rate - especially among local mothers - will remain very low, and the pace of ageing will stay rapid. The key reason for the problem is the decreasing number of marriages in Hong Kong. People are also getting married later in life. In the 1980s, only about 5 per cent of adults over the age of 45 were single, but the figure grew to 20 per cent by 2001. Statistically, it's difficult for women in Hong Kong to get married. There are more women than men here, in terms of absolute numbers. And in the age groups considered most suitable for marriage, there are 80,000 more single women than men. This is partly because a lot of Hong Kong men are marrying mainland women. Women looking for a partner here must recognise the highly competitive environment, and be reasonable about their expectations. Getting married is only one step towards parenthood. Many couples opt not to have babies, and most of them cite work pressures and finances as the reasons. A lot of people think of having a baby as a very expensive project. A recent bank advertisement on TV claimed that it costs HK$4 million to raise a child. I'm afraid that this statement will scare off some potential parents, even though it may be exaggerated. So what can be done to resolve this demographic problem? In general, we have to create a more family-friendly environment in the city - providing support for people who choose to have children. One common suggestion you hear is that the government should provide financial incentives to raise a family, such as tax allowances or a baby bonus. That addresses part of the problem. Another matter is time. Norwegians can take 52 weeks' paid parental leave, while many other countries promote flexible working hours for mothers. But there is no free lunch: all these options carry price tags. Still, it's time for us to think seriously about such an important topic: it's vital for our future. The chief executive has talked about people having three children, but that doesn't seem very practical, since so few Hongkongers would want a third child. Only 5 per cent of couples now have three or more children. The crucial thing is to get those with no youngsters to have one - or those with one child to have another. Mathematically, the change from zero to one has a huge impact. Personally, I have done my part for Hong Kong's population growth, with my three children. I am a happy parent. Paul Yip Siu-fai is a member of the support group on population policy under the Sustainable Development Council.