A population pyramid graphically illustrates the age and gender distribution of a given population. The shape of the pyramid conveys details about life expectancy, birth, fertility, and mortality rates. Additional data that can be extrapolated from a population pyramid include the effects of historical events, economic development, and future demographic trends. This information helps direct plans for the subsequent social and economic needs of a given population.
Population pyramid:
Age-gender pyramid
A graphical illustration showing the age-sex distribution of a population
Birth rate (or crude birth rate): number of live births per 1,000 population in a given year
Fertility rate: births per 1,000 women of childbearing age (aged 15–44) in a given year
Death or mortality rate (or crude death rate): number of deaths per 1,000 population in a given year
Life expectancy: average number of additional years a person could expect to live if current mortality trends were to continue for the rest of that person's life
Uses 2 juxtaposed histograms (generally 1 for each gender), turned sideways:
Vertical (y-axis):
Age of the population
Age groups displayed in the central axis
Males: left of the vertical axis
Females: right of the vertical axis
Horizontal axis (x-axis): percentage or size of the population
Illustrates a series of stacked bars, with each bar representing the population and the age group
Youngest age group: represented by the bottom bar
Oldest age group: uppermost bar
Uses of the Population Pyramid
Long-term trends of fertility and mortality rates:
Fertility rate:
Important influence on the shape of the pyramid
Represented by the width or base of the pyramid
More children = broader base
Death rate: slope of the pyramid
Life expectancy: height of the pyramid
Short-term trends and significant events:
Kinks or indents in the pyramid: indicate decline in birth rates or increase in death rates (e.g., wars, famine, disease)
Bulges in the pyramid: indicate increase in birth rates (e.g., baby booms)
Information about sex ratio of a population and effects of migration
Data on future growth of the population:
Median age of the population: lower median age, higher population growth
Population pyramid of Japan: The bulk of the population is in the 45–70-year age group. A low birth rate is exhibited by the tapering bottom of the graph.
Population pyramid of Bahrain: The pyramid shows that there are more males than females, with the majority of the population in the 25–45-year age group. This increase in the male population reflects the effect of labor Labor Labor is the normal physiologic process defined as uterine contractions resulting in dilatation and effacement of the cervix, which culminates in expulsion of the fetus and the products of conception. Normal and Abnormal Labor migration.
1950 Population pyramid of the Russian Federation. Note the kinks or indents for ages 5–9 years showing the low-birth-rate effects of World War II in the years prior. Another consequence is the lower-than-expected number of men aged 20–50 years in that period.
Future needs
Forecasts social and economic needs for national planning based on the distribution of the population's age groups:
Working-age population (15–64 years)
Children and young adolescents (under 15 years old)
Elderly population (65 years and older)
Dependency ratio:
Ratio between dependents and the working group
Higher ratio: more dependents
Youth dependency ratio:
Ratio between youth < 15 years of age and the working-age group
High youth dependency ratio: plan for housing, education, schools
Old-age dependency ratio:
Ratio between those > 65 years of age and the working-age group
High old-age dependency ratio: plan for health care, pension, nursing homes
Population Pyramid – Descriptive Epidemiology
Types of Population Pyramids
Stationary pyramid
Overall shape is a rectangle, tapering at the top.
Describes a population with:
Low fertility rate
Low mortality rate
High life expectancy
Almost equal percentages in the age groups
Indicates slow growth of the population
Seen in developed countries
Stationary population pyramid (United States) in 2017, showing even bars indicating that most age groups are almost equal in size
Expansive pyramid
Overall shape is an upright pyramid, with a broad base.
High fertility rate
High mortality rate
Low life expectancy
Each age group is smaller than the age group before it.
Indicates fast growth of the population, with small share of older people
Seen in developing countries
Expansive population pyramid (Nigeria): Note the wide base, which is indicative of a high fertility rate.
Constrictive pyramid
Overall shape is an inverted pyramid, with a narrow base.
Narrowing at the bottom of the graph indicates that the population is shrinking.
Large share of the population is aging.
Seen in wealthy, industrialized, developed countries (high literacy, good access to birth control and healthcare)
Constrictive population pyramid (Germany), showing a narrow base, indicating a low birth rate
Stages of Population Pyramids
Demographic transition model
Shows the population growth trend as it develops from a pre-industrial to an industrialized economic system
Pattern associated with:
A drop in mortality rates
An increase in population growth
A fall in birth rates as the country becomes more developed
Sequence of stages
Stage 1: high stationary
Increased birth rate
Increased mortality rate, even in younger age groups
No population growth
Stage 2: early expanding
Triangular shape
Decreasing mortality rate
Improving life expectancy
Increased rate of population growth affected by:
Improved healthcare and sanitation
Better education
Stage 3: late expanding
Dome-shaped pyramid
Decreasing birth rate and mortality rate
Population still increases but growth rate declines.
Affected by:
Technological and economic changes
Changing norms (desire for material possessions, fewer children)
Stage 4: low stationary
Barrel-shaped pyramid
Low birth and low mortality rates
Rapid growth ends.
Juvenile population almost equals the older population.
Seen in most developed countries
This stage is yet to be seen in many nations.
Low birth and mortality rates
If the fertility rate of < 2 children per woman persists → population size will decrease.
Noted in some countries (e.g., Japan, Germany):
Contracting population
Death rate has already exceeded the birth rate.
Older population: increasing more than the juvenile population
Image illustrating stages of demographic transition, with the upper graph showing an increase in population with a falling death rate. Lower illustration shows the trend of population pyramids. The birth and death rates change through different stages in the model. As the population experiences prosperity and modernization, both birth and mortality rates fall. At stage 4, the population is stable but the growth rate is declining. Stage 5 is noted in a few nations, but is yet to be seen in most countries.
Image: "Five stages of the demographic transition" by Our World in Data. License: CC BY 4.0
Principles of Epidemiology in Public Health Practice.cdc.gov. Retrieved 12 Oct 2020, from https://www.cdc.gov/csels/dsepd/ss1978/lesson4/section3.html
Federico, B., Capelli, G., Costa, G., Mackenbach, J., Kunst, A. (2012) Looking at the smoking epidemic through the lens of population pyramids: sociodemographic patterns of smoking in Italy, 1983 to 2005. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3573981/#!po=1.21951
Jones, M., Bourbeau, C. (2019) What Population Pyramids Reveal About The Past, Present And Future. https://www.wiscontext.org/what-population-pyramids-reveal-about-past-present-and-future
Population reference bureau. Glossary of demographic terms. Retrieved 14 Oct 2020, from https://www.prb.org/glossary/
Ritchie, H., Rosser, M. (2019) Age structure. Retrieved 12 Oct 2020, from https://ourworldindata.org/age-structure
Rosser, M., Ritchie, H., Ortiz-Ospina, E. (2013) World Population Growth. OurWorldInData.org. Retrieved 13 Oct 2020, from: https://ourworldindata.org/world-population-growth
Saroha, J. (2018) Types and Significance of Population pyramids. Worldwide Journal of Multidisciplinary Research and Development 4 (4): 59–69.