Population Pyramids Just Ain’t What They Used Be

What comes to mind when you think of a population pyramid? Well, if you thought of a pyramid-shaped diagram illustrating the population age distribution of a country divided by sex, you would…well…only be half right.

Population pyramids are indeed diagrams that show the breakdown of a region’s population by age and gender, however, increasingly, population pyramids are becoming less and less “pyramid-like.”

In both developed and developing countries dramatic affects on life-expectancy have forever changed age demographics and thus population distribution in population pyramids. In a typical population pyramid, the youngest segment of the population is represented at the base of the pyramid and the oldest at the top. The base is much wider than the apex of the pyramid and as one approaches the oldest members of the population, the slope of the pyramid decreases gradually on either side.

In developed nations the base of the pyramid is shrinking as couples are having fewer and fewer children. Meanwhile, dramatically increased life expectancy, like that in Japan has made it so the largest portion of the diagram is in the middle to upper section of the pyramid–making the largest group of people in the age range of 60-64!

In developing nations the picture tells a completely different story. In Zimbabwe for example, the base of the pyramid is indeed the largest portion of the pyramid, however the slope upwards to the apex of the pyramid is dramatically steep. It is almost as if the middle portion of the pyramid has literally been carved away. The shortened life expectancy in the third world has created populations predominately made up of children under the age range of 15-19. In both cases, however, women are living longer than men.

We now know that in both developing and developed nations the age distributions have dramatic implications for the not only the labor force but also the burden of disease. In other words, to best understand what diseases will affect a country the most, you have to look at the age distribution of a region. Now that we have a basic understanding of population pyramids, in my next post I hope to connect this even further to what this means in terms of public health and disease.

If you’re curious to check out the population pyramids for every country from 1950 till 2050, check out the link below!

http://www.census.gov/ipc/www/idb/country.php

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