Historically, human population planning has worked towards growing the global population. Only within the most recent century has there been concern about the effects of rapid population growth. Environmental factors that have been considered include deforestation, pollution, and contamination of water. A growing population means more resources needing to be used, and it was in the 20th century that scholars truly concerned themselves with these effects. Prior to the 20th century, they focused more on the positive effects of larger populations. Ancient societies felt that larger populations were beneficial to economic growth and for the protection of a nation. Even so, philosophers such as Confucius and Aristotle warned against rapid population growth. Having too many people too quickly would strain resources, since there would not be time to accommodate for them all. In the 16th and 17th centuries, disease and famine were prevalent and people were concerned about the rate at which the population was decreasing. During the 20th century, the invention of pill contraceptives and improvement of other contraceptives, like rubber condoms, led to a decrease in live births. These improvements plus the observed reality of the dangers overpopulation poses brought a global wave of population planning.
Many methods of population control involve reducing the number of babies born, or the crude birth rate (CDR). Some do so by altering the body of a potential parent, through sterilization or the use of birth control. Abstinence is another popular option. However, certain countries, like China, tried to reduce birth rates on a national scale by controlling the sizes of families. Their one-child policy was implemented in 1979 after a famine swept through the nation. While trying to become industrialized, the result was a reduction in food production and supply.