Since the time of the Black Plague, the world’s population has headed in only one direction: up. But within a few decades, writes Ben J. Wattenberg in his new book Fewer: How the New Demography of Depopulation Will Shape Our Future (Ivan R. Dee, October 2004), the number of people on earth will level off and then go down. In countries throughout the world—both modern and less developed—birthrates and fertility rates have fallen at an astonishing rate.  Among the modern nations, only the United States is an exception to the trend, likely to grow by about 120 million people by mid-century, principally through immigration.  What will this future of depopulation bring?  Will China and India rise to prominence? How will it affect commerce, the environment, pensions, health care, and the geopolitical balance?