Population Pyramids

The most important demographic characteristic of a population is its age-sex structure. Population pyramids (also known as age-sex pyramids) graphically display this information to improve understanding and ease comparison.

Age-sex pyramids display the percentage or actual amount of a population broken down by gender and age. The five-year age increments on the y-axis allow the pyramid to vividly reflect long term trends in the birth and death rates but also reflect shorter term baby-booms, wars, and epidemics.

 There are three key types of population pyramids:

Rapid Growth

Philippines Pyramid

This graph of the Philippine population shows a triangle-shaped pyramid and reflects a high growth rate of about 2.1%annually.

Slow Growth

U.S. Pyramid

In the United States, the population is growing at a rate of about 1.7 percent annually. This growth rate is reflected in the more square-like structure of the pyramid. Note the lump in the pyramid between the ages of about 35 to 50. This large segment of the population is the post-World War II "baby boom." As this population ages and climbs up the pyramid, there will be a much greater demand for medical and other geriatric services. An online animated population pyramid from 1950 to 2050 shows the aging of the boomers.

Negative Growth

Germany Pyramid

Germany is experiencing a period of negative growth (-0.1%). As negative growth in a country continues, the population is reduced. A population can shrink due to a low birth rate and a stable death rate. Increased emigration may also be a contributor to a declining population.