What Does Zero Population Growth (ZPG) Really Mean?

What Does Zero Population Growth (ZPG) Mean
While demographers are concerned about the population explosion, various population theorists propose a goal of zero growth as the only way to save the fast diminishing natural resources. This Buzzle post provides information on this highly debatable topic and elaborates on the meaning of 'zero population growth' or ZPG.
Alarming!
According to the United Nations Population Fund (UNFPA), it is estimated that the world population will reach 9.3 billion by 2050.
The World Bank Development Education Program states that a majority of the population in developing countries still believes in the notion of 'children are a gift from God' or 'children help continue the family line', thereby resulting in a population explosion. Whereas the developed countries are riding high on woman's liberation movements and increased abortion rates that have resulted in an imbalance between the birth and death rates prompting a fervent plea to adopt the zero population growth model.

Most demographers believe that there will be a shift in the paradigm of the developing countries as well, and the world might achieve the theorized balanced population by the turn of this century. Let us further explore this demographic phenomenon.
History
▶ Famous economist Thomas Robert Malthus in his book Essay on the Principle of Population (1798) proposed the first systematic population theory. The theory stated that human population grew at a geometric rate which is double with each cycle, while the food production would progress at an arithmetic rate.
For example, if food yield increased in a series of twenty-five year intervals in the arithmetic progression 1, 2, 3, 4, 5, 6, 7, 8, 9, in the same interval, population would increase in the geometric progression 1, 2, 4, 8, 16, 32, 64, 128, 256. This assumption of arithmetic food growth with simultaneous geometric human population growth anticipated a future with no resources to survive on. To avert such a calamity, Malthus proposed population control, this is popularly known as the Malthusian theory.
Kingsley Davis, famed American sociologist and demographer, first coined the term zero population growth.
▶ In the late '60s, ZPG became a salient political campaign in the U.S. and parts of Europe along with environmentalism and feminism. Paul Ehrlich, author of the renowned book 'The Population Bomb', stated: ''The mother of the year should be a sterilized woman with two adopted children.''
Definition
Zero population growth (ZPG) is the given condition through which human population growth remains constant by the equivalent birth and death rates.
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Explanation & Causes of Occurrence
Hungry boy
▶ The World Population Facts of the 1980s reports that about half a billion people were starving or malnourished, an additional one billion lacked access to clean water and medical care, and about one-third of the world's labor force was unemployed. Population in the Third World countries increased from 1.7 billion to 3.0 billion during 1950-1975.
All these factors contributed in the slow economic growth rate, and hence, caused concern among the demographers that the world was slowly inching towards an extinction of its natural resources. Around this time, the model of zero population growth was proposed.

▶ The fertility rate is termed as the average number of children that would be born to a woman over her lifetime. This rate in developing countries is on an overdrive, which is 4.31 children per couple - 3.09 children per couple meaning on an average a woman conceives 4 or more children in a third world country. An authoritarian ZPG policy aims to reduce this fertility rate to two children per couple in developing countries.

▶ While the third world countries still grapple with this situation, there is an opposite effect on developed countries and mainly European countries who are witnessing a fall in the fertility rate. Among the main factors that are responsible for the near zero growth of population in these countries are the institution of marriage being challenged by single parent families, the only parent being the mother, increasing divorce rates, and live-in couples. With increasing awareness and education, more and more women are opting for a career-centered life. Another cause is the increased rate of abortions arising due to the above social situation.

▶ Despite having child benefits more and more couples are opting not to have children as they consider it as a financial burden. Countries nearing zero population are Cook Islands, Bulgaria, Montenegro, Estonia, Ukraine, Latvia, Russia, Germany, Italy, China, Iceland, Japan, Ireland, Belgium, France, Luxembourg, Denmark, and Serbia.

▶ Fertility rates are declining and this trend is anticipated to proceed over the next fifty years, causing the world population to eventually stabilize approximately between 8 and 12 billion; however, this trend is still a speculation.
The United Nations estimates that if the total fertility rate of almost every country reaches 2.1 children per woman, the world population would be 9.4 billion by 2050, but if worldwide fertility declines only to 2.6 children per woman, the world population in 2050 would be 11.2 billion.
Examples
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▶ Among the third world countries, China prominently stands out for the implementation of this model and is expected to witness a zero population growth rate by 2030. This is mainly due to China's successful economic growth, improved standard of living, one child only family planning policy, late marriages, late childbearing, and the use of contraceptives. Since 1980, China has been able to successfully limit most urban couples to one child and most rural couples to two children. However, in November 2013, the government had to relax the one-child policy norm due to unpopularity, reduced labor force, and to provide support for an aging population.

▶ Japan has seen a rise in 'parasite singles', meaning an increasing number of young Japanese women are choosing to remain single, forcing the traditions of society to take a back seat. According to census estimates, in 2004, 54% of Japanese women in their 20s were still single, women are indulging in a lifestyle centered on acquaintances, workplace, and spending disposable income. This same trend can be found in men too who are shunning marriage or staying away from relationships. This phenomenon is a leading cause in the nation's declining birth rate, the government's concern has prompted it to provide incentives to couples that have minors, including disburses and free health care.

In spite of the increase in the aging populations of European and other developed nations due to the decline in fertility rate, there are other factors like immigration which effect the demographic figures of developed countries. Zero population growth is often a goal of demographic theorists and conservationists, who believe that reduction of population growth is essential for the good health of the ecosystem. Attaining a balanced population growth is still a challenge because a country's population growth is often influenced by economic factors, level of impoverishment, natural catastrophes, disease, etc.
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