"Every year Malthus is proven wrong and is buried—only to spring to life again before the year is out. If he is so wrong, why can't we forget him? If he is right, how does he happen to be so fertile a subject for criticism?" I wrote those words in the 1960s in an introduction to an anthology of essays on population. How naive I was! I supposed that the voices that were then sounding the alarm about population growth would at last get the public's attention. And so they did for about a decade during which environmentalists made common cause with populationists. But some of the most influential of the environmental activists viewed population as a dangerous and unwanted diversion from what they conceived to be humanity's true problems. Their stifling of public concern for population problems was reinforced during the Reagan years by self-styled "supply-side economists." Soon the predominent population message broadcast by both the political left and the political right was "Not to worry!" In 1968 ZPG, Inc., was founded to promote zero population growth as an ideal both for the United States and for the world. Its membership was confined mostly to 350 chapters on college campuses. Twenty-one years later, in 1989, the number had shrunk to just nine. Though Paul Ehrlich's The Population Bomb was a bestseller in 1968, worrying about population growth did not become a growth industry. Malthusians saw population growth as a "root cause" of inflation, unemployment, pollution, congestion, unwanted immigration, influxes of heartrending refugees, trade wars, drug wars, and terrorism. Each of these pathologies has many causes; anti-Malthusians belittled population. Common economic experience made it hard to believe that a population gain of 2 to 4 percent per year (which characterizes poor countries) could be serious; the less than one percent annual growth rate found in rich countries seemed even more trifling. Students of population, however, pointed out that the average gain in world population during the past million years has been less than 0.002 percent per year. That "small" rate of increase, operating over a million years, has produced our present five billion people, not a "small" number by any standard. When it comes to rates of increase that are continued indefinitely, no rate that exceeds zero by the most minute amount can be regarded as small.