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Module 8 Population Composition 119population is younger than 15, and in sub-Saharan Africa as a whole, 42 percent. Other regions, generally those that industrialized early, have a large proportion of people in the over 15 to under 65 age bracket. A growing number of affluent countries have remarkably aged populations because their birth rates are low and people live a long life. In Italy, for example, 24 percent of the people are over the traditional retirement age of 65. Many other European countries are not far behind. A population%u2019s age structure can help us predict its future population growth, allowing us to estimate how many young people will need education and employment and how many elderly people we will need to support. These numbers also help us predict consumption patterns because young people and older people have very different needs. A country with a large population of young people will likely spend a lot of money on education, while a country with many elderly people will likely spend a lot of money on health care. Age Structure 8-1 How do we describe the age structure of a%u00a0population? The age structure of a population refers to the breakdown of a population into different age groups or cohorts. For example, we may use three age groups: pre-reproductive (0%u201314 years old), reproductive (15%u201349 years of age), and post-reproductive (50 years and older), or we can divide the population into five-year age groups or cohorts (0%u20134 years, 4%u20139, 10%u201314, 15%u201319, and so on). We usually describe the age structure using percentages, but absolute numbers are fine, too. Thus, we can say that in 2020, (1) there were 73.1 million children younger than age 18 in the United States, or (2) children under 18 accounted for 22.1 percent of the U.S. population. The U.S. census is an important source of such data. As Figure 8.1 shows, age structure varies considerably among countries. Some countries have an overwhelmingly young population due to their high birth rates, which means that the proportions of the young people are relatively high. In most of the countries in Africa, as well as some countries in Latin America and tropical Asia, close to half the population is younger than 15 years old. In Niger, 49 percent of the Tropic of CancerArctic CircleTropic of CapricornEquatorPACIFICOCEANPACIFICOCEANATLANTICOCEANATLANTICOCEANINDIANOCEAN20%u00b0N20%u00b0S40%u00b0S40%u00b0N60%u00b0N80%u00b0N0%u00b020%u00b0N20%u00b0S40%u00b0S40%u00b0N60%u00b0N80%u00b0N0%u00b0160%u00b0W 100%u00b0W 80%u00b0W 60%u00b0W 40%u00b0W 20%u00b0W 0%u00b0 20%u00b0E 40%u00b0E 60%u00b0E 80%u00b0E 100%u00b0E 120%u00b0E 140%u00b0E 160%u00b0E 180%u00b0Tropic of CancerArctic CircleTropic of CapricornEquator0 2000 4000 miles0 2000 4000 kmOCEAN20%u00b0S40%u00b0S0%u00b0160%u00b0WSignificantly younger or older populations, 202340% or more are 15 yearsof age or younger15% or more are 65 yearsof age or olderOther countriesNo dataFigure 8.1 The world pattern of youth and old age. How would you describe the spatial pattern of younger national populations and older national populations? TERMS TO KNOW age structure: Refers to the breakdown of a population into different age groups or cohorts %u00a9 Bedford, Freeman & Worth Publishers. For review purposes only. Do not distribute.