In 1798 . Malthus, a British economist, put forward a theory of human population growth, (i) He stated that population grows geometrically (1, 2, 4, 8, 16, 32….) when unchecked, whereas the means of its subsistence like food grow only arithmetically (1, 2, 3, 4, 5, 6, 7….). (ii) Naturally, after some time an imbalance would occur in the population and the environment, (iii) When the imbalance reaches a certain value, some factors like hunger, epidemics, floods, earthquakes, war, etc. will bring the population to a desired level.
One frequent criticism of The Population Bomb is that it focused on spectacle and exaggeration at the expense of accuracy. Pierre Desrochers and Christine Hoffbauer remark that "at the time of writing The Population Bomb , Paul and Anne Ehrlich should have been more cautious and revised their tone and rhetoric, in light of the undeniable and already apparent errors and shortcomings of Osborn and Vogt’s analyses."  Charles Rubin has written that it was precisely because Ehrlich was largely unoriginal and wrote in a clear emotionally gripping style that it became so popular. He quotes a review from Natural History noting that Ehrlich does not try to "convince intellectually by mind dulling statistics," but rather roars "like an Old Testament Prophet."  Gardner says, "as much as the events and culture of the era, Paul Ehrlich's style explain the enormous audience he attracted." Indeed, an appearance on The Tonight Show Starring Johnny Carson helped to propel the success of the book, as well as Ehrlich's celebrity.  Desrochers and Hoffbauer go on to conclude that it seems hard to deny that using an alarmist tone and emotional appeal were the main lessons that the present generation of environmentalists learned from Ehrlich's success.
Population Register A government data collection system in which the demographic and socioeconomic characteristics of all or part of the population are continuously recorded. Denmark, Sweden, and Israel are among the countries that maintain universal registers for demographic purposes — recording the major events (birth, marriage, moves, death) that happen to each individual so that up-to-date information on the whole population is readily available. Other countries, like the United States, keep partial registers, such as social security and voter registration, for administrative purposes.