Two general misconceptions about overpopulation have achieved broad circulation. The first is that it is, as authors from Stephen Hawking to Dan Brown have written, exponential. It is not. This was a central assumption of Thomas Malthus’ “An Essay on the Principle of Population,” in which he argued that an asymmetry between population growth and food production would lead to global famine. In fact, global birthrates are in a long decline. In 1970 the average woman had nearly six children; today that number has dropped below three.The second common misconception is that rapid population growth is distributed more or less evenly across the globe. In reality, more than half of the world’s citizens now reproduce at below the replacement rate. In many countries, including the United States and India, the birthrate only just exceeds the replacement rate. Population growth remains truly high only in the developing world, mostly in Africa, the Middle East, and Latin America. Projections indicate that these regions will hold the vast majority of the world’s additional people as the century progresses. What they have in common, aside from high birthrates, is poverty.