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Population pyramid

 
Statistics Dictionary: population pyramid

A diagram (see opposite) for representing the age distribution of a population. It is really a histogram in which age is plotted vertically and frequency, or relative frequency (i.e. proportion), is plotted horizontally. Often drawn as a back-to-back pyramid with one side for males and the other side for females. Paired pyramids can be used to compare two populations.




Population pyramid. The pyramids show the age distribution, by sex, for typical European and African nations. The pyramids have the same total area, so the wide base of the African pyramid reflects the high birth-rate, and its fast-tapering shape indicates the low expectation of life.



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Encyclopedia of Public Health: Population Pyramid
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The term "population pyramid" describes the shape of a diagram showing the composition, by age and sex, of a nation's population at the time of a census. It is also called a "population profile." It is a convenient way to display in visual form the national population composition, and it is widely used by demographers, vital statisticians, public health specialists, social policy planners, and the television and print media when issues of national population are being discussed. The numbers used to construct the diagram are derived from national census returns. Because of its pyramid shape, a population pyramid is most aptly applied to a population with high birth rates and high death rates in infancy and at all subsequent ages. The term was probably coined with this in mind, because it evokes an image of small numbers in the upper age ranges perched on top of much larger numbers of newborn infants and young children. The population pyramid of a typical developing country in the mid twentieth century had this appearance. In the Philippines and Mexico, high birth rates and high death rates in infancy and childhood preserved the pyramid shape into the 1960s.

The changes in age and sex composition of the population in many industrial nations in the twentieth century altered the shape of the population profile, sometimes dramatically. The most obvious changes are due to a decline in the number of children born, plus reduced death rates at all ages up to old age. This produces a diagram better described as a population profile rather than a pyramid. It has a narrower base, a broader middle, and a blunter apex. Sharp declines in the numbers born at times of crisis such as wars and severe depressions leave a legacy of a narrowing at the middle of the profile several decades later.

Nations that suffer severe losses of young men in major wars have a profile that shows the excess of females, and this too works its way through the age groups as the cohorts of young people grow older; this is demonstrated in the 1965 profile of the United Kingdom, with the smaller numbers of middle-aged and old men than women in the same age groups reflecting the losses of the two world wars.

The most dramatic changes in the shape of the population profile may be those that are now appearing in sub-Saharan Africa, where HIV/AIDS (human immunodeficiency virus/acquired immunodeficiency syndrome) has had a devastating effect, selectively killing young sexually active men and women and leaving nations with orphan children to be raised by aged grandparents. Other changes appear in nations where high proportions of young immigrants are rapidly absorbed, or conversely in nations where there is substantial emigration of able-bodied young adults.

Population profiles or pyramids of successive census populations are a useful tool for the visual display of the changing composition of any nation's population, such as the United States and Canada throughout the twentieth century—with changes reflecting immigration, losses in the two world wars, reduced birth rates in the depression of the 1930s, and the surging birth rates of the baby boom years.

(SEE ALSO: Demography; Vital Statistics)

— JOHN M. LAST



Wikipedia: Population pyramid
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This distribution is named for the pyramidal shape of its graph.

A population pyramid, also called age-sex pyramid and age structure diagram, is a graphical illustration that shows the distribution of various age groups in a population (typically that of a country or region of the world), which normally forms the shape of a pyramid.

It typically consists of two back-to-back bar graphs, with the population plotted on the X-axis and age on the Y-axis, one showing the number of males and one showing females in a particular population in five-year age groups (also called cohorts). Males are conventionally shown on the left and females on the right, and they may be measured by raw number or as a percentage of the total population.

A great deal of information about the population broken down by age and sex can be read from a population pyramid, and this can shed light on the extent of development and other aspects of the population. A population pyramid also tells the council how many people of each age range live in the area. There tends to be more females than males in the older age groups, due to females' longer life expectancy.

Contents

Types of population pyramid

Population pyramids for 4 stages of the demographic transition model

While all countries' population pyramids differ, three types have been identified by the fertility and mortality rates of a country.

Stable pyramid - A population pyramid showing an unchanging pattern of fertility and mortality.

Stationary pyramid - A population pyramid typical of countries with low fertility and low mortality, also called a constrictive pyramid.

Expansive pyramid - A population pyramid showing a broad base, indicating a high proportion of children, a rapid rate of population growth, and a low proportion of older people. This wide base indicates a large number of children. A steady upwards narrowing shows that more people die at each higher age band. This type of pyramid indicates a population in which there is a high birth rate, a high death rate and a short life expectancy. This is the typical pattern for less economically developed countries, due to little access to and incentive to use birth control, negative environmental factors (for example, lack of clean water) and poor access to health care.

Constrictive pyramid - A population pyramid showing lower numbers or percentages of younger people. The country will have a greying population which means that people are generally older.

Young and aging populations

Generally a population pyramid that displays a population percentage of ages 1–14 over 30% and ages 75 and above under 6% is considered a "young population" (generally occurring in developing countries, with a high agricultural workforce). A population pyramid that displays a population percentage of ages 1–14 under 30% and ages 75 and above over 6% is considered an "aging population" (that of which generally occurs in developed countries with adequate health services, e.g. Australia). A country that displays all or none of these characteristics is considered neither.

Youth bulge

Median age by country. A youth bulge is evident for Africa, and to a lesser extent for South and Southeast Asia and Central America.

The expansive case was described as youth bulge by Gary Fuller (1995). Gunnar Heinsohn (2003) argues that an excess in especially young adult male population predictably leads to social unrest, war and terrorism, as the "third and fourth sons" that find no prestigious positions in their existing societies rationalize their impetus to compete by religion or political ideology.

Heinsohn claims that most historical periods of social unrest lacking external triggers (such as rapid climatic changes or other catastrophic changes of the environment) and most genocides can be readily explained as a result of a built-up youth bulge, including European colonialism, 20th-century fascism, and ongoing conflicts such as that in Darfur and terrorism.[citation needed]

One problem with this line of reasoning is that under conditions prevailing before the introduction of modern medicine, death rates were much higher than they are now, and almost all societies had youth bulges even when their population growth rate was negligible. However, they certainly did not experience such youth bulge as prevails today in some parts of the world or as prevailed in twentieth century Germany or in Africa and the Middle East nowadays.

It is not just that most periods of unrest occurred in societies with youth bulges, but that some of the pre-modern periods of any sort existed in societies with such bulges as well. Nevertheless, since the improvement of medicine and its introduction, the element of youth bulge has become far more salient than before. Therefore, perhaps it cannot explain massacres throughout human history, but it can serve as rather plausible theory to explain the terror, social unrest, and uprisings in today's society.[original research?]

Another problem is that it ignores the social consequences of poverty, corruption and mass unemployment among young males in developing countries, where most of the world's current population growth is occurring. The "youth bulge" is not an accurate predictor of social unrest, war and terrorism, because they are the product of far more complicated and interrelated set of factors ,of which demographics only plays a part. Yet, even when there are other factors and circumstance to enable mass unrest, a youth bulge is likely to be one of them.[original research?]

Youth bulge theory represents one of the most recently developed theories of war and social unrest, and has become highly influential on U.S. foreign policy as two major U.S. proponents of the theory, U.S. political scientist Jack Goldstone[1] and U.S. political scientist Gary Fuller,[2] have acted as consultants to the U.S. government.[original research?]

Middle East and North Africa

The Middle East and North Africa are currently experiencing a prominent youth bulge. Structural changes in service provision, especially health care, beginning in the 1960’s created the conditions for a population explosion, which has resulted in a population comprised primarily of younger people. It is estimated that around 65% of the regional population is under the age of 30.[3]

The Middle East has invested more in education than most other regions such that education is available to most young people.[4] However, that education has not led to higher levels of employment, and youth unemployment is currently at 25%, the highest of any single region[5]. Of this 25%, over half are first time entrants into the job market.[6]

The youth bulge in the Middle East and North Africa has been favorably compared to that of the Asian Tigers, which harnessed this human capital and saw huge economic growth in recent decades.[7] The youth bulge has been referred to by the Middle East Youth Initiative as a demographic gift, which, if engaged, could fuel regional economic growth and development

Uses of population pyramids

Main articles: Dependency ratio, and Generational accounting

Population pyramids can be used to find the number of economic dependents being supported in a particular population. Economic dependents are defined as those under 15 (children who are in full time education and therefore unable to work) and those over 65 (those who have the option of being retired). In some less developed countries children start work well before the age of 15, and in some developed countries it is common to not start work until 30 (like in the North European countries), and people may work beyond the age of 65, or retire early. Therefore, the definition provides an approximation. In many countries, the government plans the economy in such a way that the working population can support these dependents. This number can be further used to calculate the dependancy ratio in that population.

Population pyramids can be used to observe the natural increase, birth, and death rate.

See also

References

  1. ^ Goldstone, Jack A.: "Revolution and Rebellion in the Early Modern World", Berkeley 1991
  2. ^ Fuller, Gary: "The Demographic Backdrop to Ethnic Conflict: A Geographic Overview", in: CIA (Ed.): "The Challenge of Ethnic Conflict to National and International Order in the 1990s", Washington 1995, 151-154
  3. ^ Navtej Dhillon “The Role of the U.S. in the Middle East,” Congressional Briefing (May 2008)
  4. ^ Navtej Dhillon, Tarik Yousef. “Inclusion: Meeting the 100 Million Youth Challenge”
  5. ^ Middle East Youth Initiative – Employment
  6. ^ Navtej Dhillon, Tarik Yousef. “Inclusion: Meeting the 100 Million Youth Challenge” (2007)
  7. ^ “Youth – An Undervalued Asset: Towards a New Agenda in the Middle East and North Africa, Progress, Challenges and Way Forward,” Middle East and North Africa Region Human Development Department (MNSHD), The World Bank, 2007

Other References

  • Gary Fuller, "The Youth Crisis in Middle Eastern Society" (2004) download
  • Gary Fuller, The Demographic Backdrop to Ethnic Conflict: A Geographic Overview, was born in 1989 and was produced by Edward Gewin: The Challenge of Ethnic Conflict to National and International Order in the 1990s, Washington: CIA (RTT 95-10039, October), 151-154.

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Statistics Dictionary. A Dictionary of Statistics. Second edition revised. Copyright © Oxford University Press, 2008. All rights reserved.  Read more
Encyclopedia of Public Health. Encyclopedia of Public Health. Copyright © 2002 by The Gale Group, Inc. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Population pyramid" Read more