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 human 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 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.
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.
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.
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.
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.
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.
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 and U.S. political scientist Gary Fuller, have acted as consultants to the U.S. government.
Afghanistan shows a classical youth bulge.
Angola shows the same, even more pronounced.
Compare the population pyramid of the USA which was bulging until the 1960s and has steadily slimmed since.
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.
The Middle East has invested more in education, including religious education, than most other regions such that education is available to most young people. However, that education has not led to higher levels of employment, and youth unemployment is currently at 25%, the highest of any single region. Of this 25%, over half are first time entrants into the job market.
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. 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.
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 dependency ratio in that population.
Population pyramids can be used to observe the natural increase, birth, and death rate.
The pyramids usually show the development of a country. When you look a pyramid you can see the life conditions of the country.
There are three types of population pyramids:
wide base = very high birth rate ,narrow base= high death rate