Zero population growth refers to both a concept in population ecology, and to an organization that existed in the United States from 1968 to 2002.
The basic concept of zero population growth is illustrated by the equation: birth rate = death rate.
The organization Zero Population Growth was founded in 1968 by Paul R. Ehrlich, Richard Bowers, and Charles Remington, in the wake of the impact from Ehrlich's best-selling book, The Population Bomb. According to an ad in the paperback edition of that book: "Zero Population Growth Inc. is an organization which has been formed to bring the crucial issue of over-population to the attention of the general public, and more specifically, to the attention of our legislators (both state and federal): the ultimate goal of ZPG being to form a lobby group to press for legislation to implement far-reaching birth control programs, repeal of archaic legislation that runs counter to these objectives, and to press for allocation of funds for more research into population problems and research for better methods of contraception. In addition, ZPG will press for tax laws that, instead of offering incentives for having more children, will emphasize the need for population control."
By 1972, membership in ZPG had grown quickly to more than 35,000 members.
ZPG has passed into common usage as a concept perhaps prompting ZPG to change their name to Population Connection after 34 years on May 1, 2002.