Oct 29th 2009 | from the print editionFertility and living standardsLower fertility is changing the world for the betterSOMETIME in the next few years (if it hasn’t happened already) the world will reach a milestone:half of humanity will be having only enough children to replace itself. That is, the fertility rate ofhalf the world will be 2.1 or below. This is the “replacement level of fertility”, the magic numberthat causes a country’s population to slow down and eventually to stabilise. According to theUnited Nations population division, 2.9 billion people out of a total of 6.5 billion were living incountries at or below this point in 2000-05. The number will rise to 3.4 billion out of 7 billion inthe early 2010s and to over 50% in the middle of the next decade. The countries include not onlyRussia and Japan but Brazil, Indonesia, China and even south India.The move to replacement-level fertility is one of the most dramatic social changes in history. Itmanifested itself in the violent demonstrations by students against their clerical rulers in Iran thisyear. It almost certainly contributed to the rising numbers of middle-class voters who backed theincumbent governments of Indonesia and India. It shows up in rural Malaysia in richer, emptiervillages surrounded by mechanised farms. And everywhere, it is changing traditional family life byenabling women to work and children to be educated. At a time when Malthusian alarms areringing because of environmental pressures, falling fertility may even provide a measure ofreassurance about global population trends.The fertility rate is a hypothetical, almost conjectural number. It is not the same as the birth rate,which is the number of children born in a year as a share of the total population. Rather, itrepresents the number of children an average woman is likely to have during her childbearingFertility and living standards: Go forth and multiply a lot less | The Economist http://www.economist.com/node/14743589/print1 of 6 5/18/2011 2:11 PMyears, conventionally taken to be 15-49.If there were no early deaths, the replacement rate would be 2.0 (actually, fractionally higherbecause fewer girls are born than boys). Two parents are replaced by two children. But a daughtermay die before her childbearing years, so the figure has to allow for early mortality. Since childmortality is higher in poor countries, the replacement fertility rate is higher there, too. In richcountries it is about 2.1. In poor ones it can go over 3.0. The global average is 2.33. By about2020, the global fertility rate will dip below the global replacement rate for the first time.Modern Malthusians tend to discount the significance of falling fertility. They believe there are toomany people in the world, so for them, it is the absolute number that matters. And that number isstill rising, by a forecast 2.4 billion over the next 40 years. Populations can rise while fertilitydeclines because of inertia, which matters a lot in demography. If, because of high fertility inearlier generations, there is a bulge of women of childbearing years, more children will be born,though each mother is having fewer children. There will be more, smaller families. Assumingfertility falls at current rates, says the UN, the world’s population will rise from 6.8 billion to 9.2billion in 2050, at which point it will stabilise (see chart 1).Behind this is a staggering fertility decline. In the 1970s only 24countries had fertility rates of 2.1 or less, all of them rich. Now thereare over 70 such countries, and in every continent, including Africa.Between 1950 and 2000 the average fertility rate in developingcountries fell by half from six to three—three fewer children in eachfamily in just 50 years. Over the same period, Europe went from thepeak of the baby boom to the depth of the baby bust and its fertilityalso fell by almost half, from 2.65 to 1.42—but that was a decline ofonly 1.23 children. The fall in developing countries now is closer towhat happened in Europe during 19th- and early 20th-centuryindustrialisation. But what took place in Britain over 130 years(1800-1930) took place in South Korea over just 20 (1965-85).Things are moving even faster today. Fertility has dropped further in every South-East Asiancountry (except the Philippines) than it did in Japan. The rate in Bangladesh fell by half from six tothree in only 20 years (1980 to 2000). The same decline took place in Mauritius in just ten(1963-73). Most sensational of all is the story from Iran.When the clerical regime took over in 1979, the mullahs, apparently believing their flock shouldgo forth and multiply, abolished the country’s family-planning system. Fertility rose, reachingseven in 1984. Yet by the 2006 census the average fertility rate had fallen to a mere 1.9, and just1.5 in Tehran. From fertility that is almost as high as one can get to below replacement level in 22years: social change can hardly happen faster. No wonder the explosion on the streets of Iran thisyear seemed like a clash between two worlds: 15-29 year-olds, one-third of the population, bettereducated and with different expectations, against the established regime and the traditionalists.Why has fertility fallen so fast, so widely? Malthus himself thought richer people would have morechildren and, as any biologist will tell you, animal populations increase when there is more foodaround.To understand why wealthy people differ from well-fed animals, imagine yourself a dirt-poor(male) peasant 50 years ago. Your fields are in the middle of nowhere. Your village has no school,hospital or government services, certainly no pensions. Few goods come into it from outside,though disease is rampant and security fragile. Ploughing and reaping are done by hand. But if theFertility and living standards: Go forth and multiply a lot less | The Economist http://www.economist.com/node/14743589/print2 of 6 5/18/2011 2:11 PMharvest is normal, you usually have enough to go round. In these circumstances, the benefit of anextra pair of hands to gather the harvest outweighs the cost of feeding an extra mouth (whichanyway falls on your wife more than you). And when you can no longer work in the fields, yourchildren will be the only ones to look after you. In such a society, all the incentives point tohaving large families.The abandoned hamletNow imagine you are a bit richer. You may have moved to a town, or your village may havegrown. Schools, markets and