Zero population growth
Encyclopedia
Zero population growth, sometimes abbreviated ZPG (also called the replacement level of fertility), is a condition of demographic balance where the number of people in a specified population neither grows
nor declines
, considered as a social aim.
According to some, zero population growth is the ideal towards which countries and the whole world should aspire in the interests of accomplishing long-term environmental sustainability
.
The American sociologist
and demographer
Kingsley Davis
is credited with coining the term but it was used earlier by George Stolnitz, who stated that the concept of a stationary population dated back to 1693. A mathematical description was given by James Mirrlees
.
In the late 1960s ZPG became a big political movement in the U.S. and parts of Europe, with strong links to environmentalism
and feminism
. Yale University
was a stronghold of the ZPG activists who believed “that a constantly increasing population is responsible for many of our problems: pollution, violence, loss of values and of individual privacy.” Founding fathers of the movement were Paul Ehrlich
, author of The Population Bomb
, and Thomas Eisner
. Ehrlich stated: “The mother of the year should be a sterlized woman with two adopted children.”
of a population equals the death rate, i.e. replacement level is met and rate is stable. Unstable rates can lead to drastic changes in population levels. (This ignores migration
, which is valid for the planet as whole, but not necessarily for a nation.) A population that has been growing in the past will have a higher proportion of young people. As it is younger people who have children, there is large time lag between the point at which the birth rate falls below the death rate and the point at which the population stops rising.
Conversely, a large elderly generation can be the result of an aging “baby boom
”, but if that generation had failed to replace its population during its fertile
years, the result is a subsequent “population bust”, or decrease in population, as that older generation dies off. This effect has been termed birth dearth
. In addition, if a country's fertility is at replacement level, and has been that way for (at least) several decades (to adjust for changes in age distribution), then that country's population could still experience coincident growth due to continuously increasing life expectancy, even though the population growth is likely to be smaller than it would be from natural population increase.
Zero population growth is often a goal of demographic planners and environmentalist
s who believe that reducing population growth is essential for the health of the ecosphere
. Preserving cultural traditions and ethnic diversity is a factor for not allowing human populations levels or rates to fall too low. Achieving ZPG is difficult because a country's population growth is often determined by economic factors, incidence of poverty, natural disasters, disease, etc.
However, even if there is zero population growth, there may be changes in demographics of great importance to economic factors
, such as changes in age distribution
.
Population growth
Population growth is the change in a population over time, and can be quantified as the change in the number of individuals of any species in a population using "per unit time" for measurement....
nor declines
Population decline
Population decline can refer to the decline in population of any organism, but this article refers to population decline in humans. It is a term usually used to describe any great reduction in a human population...
, considered as a social aim.
According to some, zero population growth is the ideal towards which countries and the whole world should aspire in the interests of accomplishing long-term environmental sustainability
Sustainability
Sustainability is the capacity to endure. For humans, sustainability is the long-term maintenance of well being, which has environmental, economic, and social dimensions, and encompasses the concept of union, an interdependent relationship and mutual responsible position with all living and non...
.
History
A loosely defined goal of ZPG is to match the replacement fertility rate, which is the average number of children per woman which would hold the population constant. This replacement fertility will depend on mortality rates and the sex ratio at birth, and varies from around 2.1 in developed countries to over 3.0 in some developing countries.The American sociologist
Sociology
Sociology is the study of society. It is a social science—a term with which it is sometimes synonymous—which uses various methods of empirical investigation and critical analysis to develop a body of knowledge about human social activity...
and demographer
Demography
Demography is the statistical study of human population. It can be a very general science that can be applied to any kind of dynamic human population, that is, one that changes over time or space...
Kingsley Davis
Kingsley Davis
Kingsley Davis , identified by the American Philosophical Society as one of the most outstanding social scientists of the twentieth century, was a Hoover Institution senior research fellow and internationally recognized American sociologist and demographer...
is credited with coining the term but it was used earlier by George Stolnitz, who stated that the concept of a stationary population dated back to 1693. A mathematical description was given by James Mirrlees
James Mirrlees
Sir James Alexander Mirrlees is a Scottish economist and winner of the 1996 Nobel Memorial Prize in Economic Sciences. He was knighted in 1998....
.
In the late 1960s ZPG became a big political movement in the U.S. and parts of Europe, with strong links to environmentalism
Environmentalism
Environmentalism is a broad philosophy, ideology and social movement regarding concerns for environmental conservation and improvement of the health of the environment, particularly as the measure for this health seeks to incorporate the concerns of non-human elements...
and feminism
Feminism
Feminism is a collection of movements aimed at defining, establishing, and defending equal political, economic, and social rights and equal opportunities for women. Its concepts overlap with those of women's rights...
. Yale University
Yale University
Yale University is a private, Ivy League university located in New Haven, Connecticut, United States. Founded in 1701 in the Colony of Connecticut, the university is the third-oldest institution of higher education in the United States...
was a stronghold of the ZPG activists who believed “that a constantly increasing population is responsible for many of our problems: pollution, violence, loss of values and of individual privacy.” Founding fathers of the movement were Paul Ehrlich
Paul R. Ehrlich
Paul Ralph Ehrlich is an American biologist and educator who is the Bing Professor of Population Studies in the department of Biological Sciences at Stanford University and president of Stanford's Center for Conservation Biology. By training he is an entomologist specializing in Lepidoptera , but...
, author of The Population Bomb
The Population Bomb
The Population Bomb was a best-selling book written by Paul R. Ehrlich and his wife, Anne Ehrlich , in 1968. It warned of the mass starvation of humans in the 1970s and 1980s due to overpopulation, as well as other major societal upheavals, and advocated immediate action to limit population growth...
, and Thomas Eisner
Thomas Eisner
Thomas Eisner was a German-American entomologist and ecologist, known as the "father of chemical ecology."He was a Jacob Gould Schurman Professor of Chemical Ecology at Cornell University, and Director of the Cornell Institute for Research in Chemical Ecology...
. Ehrlich stated: “The mother of the year should be a sterlized woman with two adopted children.”
Effects
In the long term, zero population growth can be achieved when the birth rateBirth rate
Crude birth rate is the nativity or childbirths per 1,000 people per year . Another word used interchangeably with "birth rate" is "natality". When the crude birth rate is subtracted from the crude death rate, it reveals the rate of natural increase...
of a population equals the death rate, i.e. replacement level is met and rate is stable. Unstable rates can lead to drastic changes in population levels. (This ignores migration
Human migration
Human migration is physical movement by humans from one area to another, sometimes over long distances or in large groups. Historically this movement was nomadic, often causing significant conflict with the indigenous population and their displacement or cultural assimilation. Only a few nomadic...
, which is valid for the planet as whole, but not necessarily for a nation.) A population that has been growing in the past will have a higher proportion of young people. As it is younger people who have children, there is large time lag between the point at which the birth rate falls below the death rate and the point at which the population stops rising.
Conversely, a large elderly generation can be the result of an aging “baby boom
Baby boom
A baby boom is any period marked by a greatly increased birth rate. This demographic phenomenon is usually ascribed within certain geographical bounds and when the number of annual births exceeds 2 per 100 women...
”, but if that generation had failed to replace its population during its fertile
Fertility
Fertility is the natural capability of producing offsprings. As a measure, "fertility rate" is the number of children born per couple, person or population. Fertility differs from fecundity, which is defined as the potential for reproduction...
years, the result is a subsequent “population bust”, or decrease in population, as that older generation dies off. This effect has been termed birth dearth
Birth dearth
Birth dearth is a neologism referring to falling fertility rates. In the late 1980s, the term was used in the context of American and European society. The use of the term has since been expanded to include many other industrialized nations. It is often cited as a response to overpopulation, but...
. In addition, if a country's fertility is at replacement level, and has been that way for (at least) several decades (to adjust for changes in age distribution), then that country's population could still experience coincident growth due to continuously increasing life expectancy, even though the population growth is likely to be smaller than it would be from natural population increase.
Zero population growth is often a goal of demographic planners and environmentalist
Environmentalist
An environmentalist broadly supports the goals of the environmental movement, "a political and ethical movement that seeks to improve and protect the quality of the natural environment through changes to environmentally harmful human activities"...
s who believe that reducing population growth is essential for the health of the ecosphere
Ecosphere
Ecosphere has several different meanings:* In ecology the term ecosphere can refer to the Earth's spheres, a planetary ecosystem consisting of the atmosphere, the geosphere , the hydrosphere, and the biosphere....
. Preserving cultural traditions and ethnic diversity is a factor for not allowing human populations levels or rates to fall too low. Achieving ZPG is difficult because a country's population growth is often determined by economic factors, incidence of poverty, natural disasters, disease, etc.
However, even if there is zero population growth, there may be changes in demographics of great importance to economic factors
Demographic gift
Demographic gift is a term in demographics used to describe the initially favorable effect of falling fertility rates on the age dependency ratio, the fraction of children and aged as compared to that of the working population.-Overview:...
, such as changes in age distribution
Population pyramid
A population pyramid, also called an age structure diagram, is a graphical illustration that shows the distribution of various age groups in a population , which forms the shape of a pyramid when the population is growing...
.
In China
China is the largest country by population in the world, being home to 1.3 billion people. China is expected to witness a zero population growth rate by 2030. China's population growth has slowed since the beginning of this century. It is because China's family planning policy, which was formulated in the early 1970s, encourages late marriages and late childbearing, and limits most urban couples to one child and most rural couples to two children. Without the policy, the country's population would be 400 million more than the current 1.3 billion people. According to the government projection, the work-age population will then drop to 870 million. The Chinese government is hoping to see the zero population growth in the future.See also
- Birth creditBirth creditA "choice-based, marketable, birth license plan" or "birth credits" for population control has been promoted by urban designer and environmental activist Michael E. Arth since the 1990s...
- Demographic transitionDemographic transitionThe demographic transition model is the transition from high birth and death rates to low birth and death rates as a country develops from a pre-industrial to an industrialized economic system. The theory is based on an interpretation of demographic history developed in 1929 by the American...
—Zero population growth is achieved when the birth rate of a population equals in a situation where net migration is also zero - OverpopulationOverpopulationOverpopulation is a condition where an organism's numbers exceed the carrying capacity of its habitat. The term often refers to the relationship between the human population and its environment, the Earth...
—when an organism's numbers exceed the carrying capacity of its habitat. - Population Matters (formerly known as the Optimum Population Trust)—A registered United Kingdom charity, think tank and campaign group
- Steady state economy
- Z.P.G.Z.P.G.Z.P.G. is a British science fiction film that was released in 1972, in the wake of Paul R. Ehrlich's best-selling book The Population Bomb. The film concerns an overpopulated, very polluted future Earth, whose world government executes those who violate a 30-year ban on procreation...
—A science-fiction movie concerning the topic of zero population growth. - Zero growthZero growthZero growth is a theory that all economic activities and policies should be oriented towards achieving a state of equilibrium, a steady state economy....
External links
- Population Connection
- Enviro, Population Movements Merge Goals for Healthier Planet
- World Watch Institute
- Northwest Environment Watch
- Center for Environment and Population—Science, Policy, and Public Education on Population and the Environment