Beijing's one-child policy is abhorrent. But its critics are guilty of gross exaggeration. Despite what they claim, the effect of the one-child policy on China's population and economy has been small. Beijing's heavy-handed approach to family planning is in the news again after local officials in Shaanxi forced a seven-months pregnant woman to have an abortion because she already had a child. But it isn't grotesque outrages like the Shaanxi case that worry Beijing's policy advisers so much as the supposed demographic effects of the one-child policy. According to conventional wisdom, the one child per family limit, imposed back in 1979 by Beijing, was a desperate attempt to slow China's ballooning population growth. It may have been harsh, but over the subsequent decades it prevented hundreds of millions of extra births, successfully averting a Malthusian catastrophe and paving the way for China's economic boom. Now, however, academics are beginning to worry that the policy has been too effective at suppressing China's birth rate. Unless people are allowed to have more babies soon, they warn that the country's labour force will plummet in future years and that China will not be able to support its rapidly ageing population as the current generation of workers reaches retirement. They are certainly right that China's fertility rate is low. In the late 1960s, the average woman could expect to bear six children over the course of her lifetime. By 2010, that number had plunged to just 1.6, well below the 2.1 rate needed to maintain population numbers. But as the first chart shows, the big fall in China's birth rate took place in the mid-1970s, before the imposition of Beijing's draconian family planning laws. What's more, in the 10 years following the policy's introduction, the fertility rate barely changed. As a result, it is clear that those who blame China's low birth rate on the one-child policy are barking up the wrong tree. The policy didn't cause the fall in fertility rates, and scrapping it now won't lead to a baby boom. In reality, the fall in China's birth rate simply followed a path already trodden by other East Asian countries as their economies developed. As populations move from the countryside to cities, education standards improve and household incomes rise, fertility rates decline. In short, wealthy, well-educated women who live in cities have fewer children, have them later in life and leave longer intervals between each birth. That's partly because children are expensive. According to Janet Zhang at research company Dragonomics, it typically costs between 2,000 and 6,000 yuan a month to send a preschooler to a Beijing kindergarten. In a city where household disposable income averages about 10,000 yuan a month, having two children is beyond the means of the majority of families. In cities where housing is expensive and flats are small, the costs are compounded. And with working-age adults expected to provide for their retired parents as well as pay for the education of their children, the tendency to have fewer children is further reinforced. For many couples, the cost of moving to a bigger flat to house a second child, while looking after four retired parents, is prohibitively high. Ditching the one-child policy won't make any difference. If you don't believe that, just look at Hong Kong and Macau. Neither has a one-child policy. But both are wealthy, well-educated and highly urban societies with high property prices. And according to the World Bank, they have the lowest fertility rates in the entire world (see the second chart). So yes, get rid of the one-child policy to prevent abuses like the one that occurred in Shaanxi. But don't think that scrapping it will solve China's demographic problems.