During the 1960s and 70s, the world population was growing at 2% annually--a rate that would double the world's population about every 30 years, according to Wang Fen at New Scientist. China led the way, becoming the world's most populous country and among its youngest--with nearly a third of its population under 15-years-old in 1982. The Chinese government issued its infamous one-child policy in 1980 with an eye toward controlling the population bomb and raising the country's living standards. Fen contends that the move was pretty much "bad science combined with bad politics." And that the bomb that never went off--population growth has slowed measurably--wasn't defused by policy as much as falling fatality levels. When children live longer, world trends indicate, people have fewer of them. By this theory the boom in childbirth was partially just a hedge against disaster. When you eliminated some of the potential for disaster--giant world wars, disease, famine--couples choose not to have extra children.
The rule has been relaxed various times since its implementation. It's now legal for a Chinese couple to have two children, if one of the partners is an only child--a likelihood given the one-child policy's legacy. Now China is considering abolishing the restriction, if only to counterbalance its top-heavy elderly population--the inverse, of course, of the situation 30 years ago. As Fen points out, it is in myriad ways a startlingly different China today--with 50% of the population now urban dwellers (China was mainly an agrarian economy a half century ago) and education levels rising. Correspondingly Chinese young adults are making choices that resemble those of their urban Western counterparts: later marriages and early career focus. In Shanghai, China's largest city, the average fertility rate--despite the relaxation of the rule--is well below one child, at 0.7 children per couple. The law--if and when it changes--will lag behind the facts it's meant to influence. As in the rest of China and elsewhere, huge economic changes are altering behavior faster than any rules.