An impressively well-balanced account of a life-or-death issue: Is each new person an asset or a liability to life on earth? Newton contrasts the pessimistic ideas of the 60's and 70's with some ``mixed'' views and the more optimistic predictions of Julian Simon. Blending real examples, authoritative facts, fictionalized scenarios, and well-chosen quotes from experts, he elucidates the basic conflicts and explains why ``doomsday'' predictions continue to arise. Throughout, he refuses to take sides, advising readers to stick to the facts. Concise and accessible, with technical, social, and political terms fully defined. A few b&w photos; clear, useful charts and tables. Source notes; bibliography; index. (Nonfiction. 12+)