Population Pyramids: A Window into Demographic Evolution


Population Pyramids Population Pyramid
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The population pyramid depicts the gender and age split of the population at a specific moment in time. It is made up of two histograms, one for each gender (by convention, males on the left and women on the right), with numbers displayed horizontally and ages displayed vertically. The numbers by gender and age are determined by the interplay of fertility, death, and migrations. The form of the pyramid and its fluctuations throughout time are mostly determined by changes in fertility.


A population pyramid, also known as “age-sex pyramid,” is a graphical representation of the distribution of a population (usually that of a nation or part of the world) by age groups and sex; when the population is expanding, it typically assumes the shape of a pyramid. Males are often depicted on the left, while females are depicted on the right, and they can be quantified in absolute numbers or as a proportion of the overall population. The pyramid can be used to depict the age of a certain population. It is also used in ecology to calculate the total age distribution of a population, which is an indication of a species’ reproductive capability and chances of survival.

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A population pyramid depicts the population size under examination on the horizontal axis and age on the vertical axis. The result is a sequence of bars piled on top of one another, each indicating an age category (usually in 5-year age groups), with the lowest bar representing the youngest age group and the highest bar representing the oldest age group. The horizontal length of each bar shows the number of people in the represented population’s specific age group. The age groups associated with each bar are shown along the center axis, one side, or both sides of the graph. The years of birth for each age category are frequently stated on the graph. To ensure proportionality, the age groupings are all the same size (e.g., one year, five years, or ten years), and the bars are all the same height. Depending on the statistics available for the population portrayed, the age (vertical) axis is frequently terminated at the age group 80 to 84. For certain populations, statistics for older age groups are partial or erroneous, or there are a small number of persons in the older age groups. Population pyramids for comparison should be drawn at the same scale and show the same age groups.

The population pyramid may be used to depict other demographic attributes including marital status, race, or geographical area. The bar for each age-sex group is further split in this example to indicate the extra categories. The formatting scheme used to represent the extra categories should be utilized consistently all through the graph, and the same order should be used on both sides of the vertical axis, in mirror image format. For example, if race is displayed and the divisions are white, black, and other, the classifications for men and females would be placed in the same sequence, working outward from either side of the center axis.


The population pyramid’s shape effectively communicates significant information about a population’s age-sex composition. A broad-based pyramid implies that individuals in the younger age groups make up a relatively high proportion of the population, whereas a narrow or pointed top suggests that people in the older age groups make up a relatively small part of the population. The number of girls in older age groups in many societies is substantially larger than the number of men; this is represented in the form of the pyramid, with the bars on the right side of the central axis (the female side) being longer than those on the left (male side). The age group (bar) indicated by the point on the vertical axis that evenly divides the area within the pyramid would be the population’s median age (equal areas within the pyramid fall above and below the age represented by the bar).

The form of the population pyramid also reflects population fertility and death. A large base with sharply tapering sides (a real pyramid form) indicates high fertility and high death rates in younger age groups. Irregularities in the population pyramid’s profile transmit information about population shifts or aberrations. A bulge or depression in the shape of the population pyramid may imply exceptionally high fertility or death, or population fluctuations as a result of immigration or emigration.


The shape of population pyramids efficiently conveys information about a population’s age-sex composition. Birth rates are shown by the breadth of the base. A broad-base pyramid suggests that birth rates are high and that the population is concentrated in the lower age groups. In the case of growing pyramids, the base is the widest, indicating that population growth rates will stay high in the near future as this population shifts to reproductive age groups. A thin or pointed top suggests that the elderly make up a tiny share of the population. A large base and steeply tapering sides imply high fertility and high death rates in the population’s lower age groups, such as high newborn mortality rates and high child mortality rates.

By measuring the ratio of the total of the juvenile and senile populations to the working population, population pyramids may be used to estimate the number of economic dependents. LDC pyramids indicate more youthful dependents, whereas MDC pyramids show more senior dependents. The population pyramid with a higher share of young dependents has a very triangular shape (true pyramid type), whereas the pyramid with a nearly equal share of juvenile and reproductive age groups and a fair share of elderly population, with falling birth rates and rising life expectancy, will change shape from triangular to barrel-type. They are mirrored in the pyramid’s form. In senior age groups, the number of females in majority populations is far larger than the number of males. It is indicated by the longer bars on the right side of the central axis (the feminine side) vs the left (male) side. The median age of the population may be calculated using the age group (bar) on the vertical axis that splits the pyramid’s area into two equal sections.


Demographers who have researched historical changes in the world’s population’s age and gender composition, fertility, and mortality have developed a theory of demographic transition. This hypothesis gives a good representation of the historical modifications in populations around the world. This shift is indicated by significantly divergent demographic pyramids. 

Stage 1 is depicted as a sharply tapering pyramid on a broad base, indicating strong fertility and high mortality among the younger age groups. Because of high mortality, the population grows slowly and remains tiny.

 The population pyramid form for Stage 2 of the population boom represents a drop in mortality, particularly among the youngest age groups, along with high fertility; the population grows swiftly but remains relatively youthful. 

The population pyramid that represents Stage 3 in the demographic transition has nearly vertical sides, a broad base, and a sufficiently wide peak, reflecting reduced fertility, reduced childhood mortality, and increased survival; older age groups make up a larger proportion of the population than in earlier stages, and population size stabilizes.


The population pyramids come in a variety of forms. Different nations have distinct demographic pyramids, and the geometry of the same countries changes over time. As a result, population pyramids have spatio temporal fluctuations. The form of population pyramids, as graphical representations, is ultimately determined by the age and gender composition of a certain community. These forms might be triangular pyramids, columnar or rectangular (with vertical sides rather than sloping sides), or irregular in profile. The primary types of population pyramids are as follows:


The expansive pyramid is a population pyramid with a large base and a progressive fall in the percentage of the population of higher age groups. This pyramid depicts a situation with high fertility, high mortality, short life expectancy, greater population growth rates, and a low proportion of elderly people. It denotes population expansion since the size of each cohort grows bigger than the size of the preceding one. Expansive age pyramids are widespread in developing nations, particularly those in Africa and Asia.


A pyramid is said to be stationary when the population share in different age groups remains consistent throughout time. It depicts a low fertility, low mortality, and high life expectancy condition. It denotes moderate population increase or population stability. The juvenile and adult age groups are represented in almost similar proportions in the stationary or near-stationary population pyramid.


A constricted pyramid is a pyramid with a narrow base. It denotes low fertility, low mortality, high life expectancy, and population aging. It is often linked with highly developed countries that have a high level of literacy, easy access to birth control techniques, and excellent health and medical facilities.


A youth bulge, according to Gary Fuller (1995), is a form of expanded pyramid. According to Gunnar Heinsohn (2003), an excess of young adult male population predictably leads to social discontent, conflict, and terrorism, as “third and fourth sons” who do not find coveted places in their current societies excuse their drive to compete by religion or political ideology.

According to Heinsohn, most historical periods of social unrest that lack external catalysts (such as abrupt climate changes or other catastrophic changes in the environment) and most genocides may be easily explained as the outcome of a built-up youth bulge.

This component has also been utilized to account explain the events of the Arab Spring. Economic recessions, such as the 1930s Great Depression and the late-2000s recession, are also said to be caused in part by a huge young population that cannot find work. The youth bulge is one reason among several in explaining societal instability and upheavals. According to a 2016 study, youth bulges enhance the likelihood of non-ethnic civil wars but not ethnic civil wars. A high number of teenagers joining the labor market and electorate puts strain on the economy and polity, both of which were built for smaller populations. Unless new possibilities are developed soon enough, this leads to unemployment and alienation – in which case a ‘demographic dividend’ accrues since productive employees outnumber young and old dependents. Nonetheless, the age range of 16–29 is connected with risk-taking, particularly among men. Youth bulges in developing nations are generally connected with increased unemployment and, as a result, a higher risk of violence and political instability. According to Cincotta and Doces (2011), the move to more mature age structures is nearly a must for democratization.

To counteract the consequences of youth bulges, particular strategies such as increased job creation, improved family planning programs, and lower overall infant death rates should be prioritized.

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The Middle East and North Africa are witnessing a significant youth bulge “Countries in the Middle East have seen a significant growth in the size of their young populations in recent decades, both in total numbers and as a proportion of the total population. Today, approximately 111 million people aged 15 to 29 live in the region, accounting for nearly 27 percent of the total population.” Beginning in the 1960s, structural changes in service supply, particularly health care, established the circumstances for a demographic explosion, resulting in a population dominated by young people. Around 65 percent of the regional population is anticipated to be under the age of 25. 

The Middle East and North Africa’s youth bulge has been compared favorably to that of East Asia, which has harnessed this people resource and seen massive economic expansion in recent decades. The Middle East Youth Initiative has described the youth bulge as a demographic gift that, if capitalized on, could fuel regional economic growth and development. “While the growth of the youth population imposes supply pressures on education systems and labor markets, it also means that a growing share of the overall population is made up of those considered to be of working age; and thus, not dependent on the economic activity of others.” As a result, the lowering dependence ratio might boost overall economic development, resulting in a demographic dividend. The capacity of a specific economy to capture this dividend, on the other hand, is contingent on its ability to assure the deployment of this expanding working-age population toward productive economic activity, as well as to produce the employment required for the growing labor force.”


Irregularities in the population pyramid’s profile suggest concerning population changes or anomalies a swell or a bulge. The profile indentation shows atypical alterations associated with high birth or death rates, or population fluctuations as a result of either immigration or emigration.


The term “baby boom” refers to a significant increase in birth rates. The word was initially used to characterize the post-second world war population expansion caused by rising birth rates, mostly from 1946 to 1964. Figure 7 depicts the population pyramids of the United States in the past, present, and future. It depicts the evolution of the baby boomer cohorts from 1960 to 2040. By 2040, the pyramid will be a column or barrel, i.e. the bottom of the pyramid, because birth rates in all cohorts will be lower than mortality rates. Along with the ageing of the population, it also indicates a comparatively greater proportion of women in elderly age groups.


Because it is a recreational county, the demographic pyramid displays a high concentration of people in the upper age categories, and internal movement of elderly people has contributed to this. Similarly, the concentration of people between the ages of 20 and 25 in Centre County, Pennsylvania, USA, is attributable to the existence of several institutions and colleges in this nation.

The age and gender pyramid of Indian immigrants in the United States is “diamond-shaped,” and it corresponds to the total number of foreign-born people. This is attributable to the immigration of working-age people between the ages of 20 and 54.


  • It is a simple and easy method to give an overview.
  • It can easily enable comparisons of population for various countries.
  • It has a variety of useful information for planning purposes. E.g. sectoral interventions
  • It can give detailed information about the age and gender of a country’s population.
  • Government can use the information to make decisions to meet the population’s needs.


  • It is, usually, not possible to distinguish the relative contributions of different demographic processes to population age structure.
  • Numbers can be too great to represent accurately.
  • It does not allow juveniles or immature forms.
  • It includes every organism irrespective of their size making the pyramid inverted.
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