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population pyramid

  A diagrammatic representation of the age and sex structure of a population (see figure). The vertical axis represents age groups — with males on the left and females on the right — and the horizontal axis indicates the numerical or percentage distribution for each sex. The population pyramid is a reflection of past and current demographic trends and also provides some indication of future demographic structures. A population whose pyramid has a broad base and narrows quickly upwards, for example, is young and highly fertile. The figure for France is more typical of populations of the developed world. It shows the general influence of ageing, which, because of lower male life expectancy, produces a strong excess of women in the over 70 age groups. The recent decline in birth rates is also evident in the shortfall in those aged under 25 years. The demographic consequences of war are also apparent in the pyramid, e.g. the sharp decline in births during the First World War is reflected in the shortfall in the numbers of people in their late 70s and early 80s. In countries of the developing world, population pyramids are more steep-sided, reflecting higher fertility, which adds people to the base of the pyramid, and higher mortality through the life course, which steadily removes them. The dependency ratio is one measure that may be derived from the study of age-sex pyramids. Pyramids may also be constructed for sub-groups within a population, reflecting distinctive demographic structures associated with particular geographical areas (for example, inner cities or remote rural districts) or with ethnicity or other characteristics. (PEO)

{img src=show_image.php?name=bkhumgeofig53.gif }

Population Pyramid France, 1897-1997 (Lévy, 1998, p.4).

Reference Lévy, M.L. 1998: La population de la France, 1995-1997. Population et Sociétés 333: 1-4.

Suggested Reading Daugherty, H.G. and Kammeyer, K.C.W. 1995: An introduction to population, 2nd edn. New York and London: Guilford, ch. 5. Petersen, W. 1975: Population, 3rd edn. London and New York: Collier-Macmillan, ch. 3.



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