Studies in demography are not common fare for that mythical creature, the general reader; this collection, however, deserves to become an exception to the dictum. These 17 essays were written over the past ten years, and while they range in subject matter from the socialist positions on birth control to family subsidies in the Netherlands or the basis of U.S. immigration policy, there is one unifying factor throughout: a steady eye upon the policy implications of the figures and theories involved. The volume is divided into two distinct halves, with the first devoted to the general topics of family planning and the population explosion, while the second is given over to the large questions of migration and acculturation. It must be emphasized these investigations are fascinating and much more accessible than they may sound. In his statistical approaches to such things as racial prejudice, religion, and city planning, Mr. Petersen has many new and important insights to offer. It will also surprise many readers that Malthus has been considerably maligned, and that Keynes owed him a great debt. The graphs and tables are here, but sparingly, since the author is one of the few social scientists who is not only in full command of his subject but the English language as well.