Variations of demographic patterns and trends range from very high fertility to sub-replacement fertility situations, from very young to aging populations, and from immigration-open to immigration-shy countries. This book, authored by John F. May, concludes that population policies are more necessary and relevant than ever for developed and developing countries. Demographers have the responsibility to promote “public demography”, namely to reach public audiences with demographic analyses and summaries of research results, as well as discuss the meaning of those results and the actions, if any, to be taken by public authorities. Countries that have adopted population policies have been able to influence their demographic outcomes and have generally reaped substantial benefits from doing so.