4 Population
The sex ratio is the number of males per 100 females in a population: l Male births consistently exceed female births due to a combination of biological and social reasons. l After birth, the gap generally begins to narrow until eventually females outnumber males, as at every age male mortality is higher than female mortality. l A report published in China in 2002 recorded 116 male births for every 100 female births due to the significant number of female fetuses aborted by parents intent on having a male child.
Dependency ratio is the ratio of the number of people under 15 and over 64 years to those aged 15–64.
number aged 0–14 + number aged over 64 number aged 15–64
The dependency ratio
Dependants are people who are too young or too old to work. The dependency ratio is the relationship between the working or economically active population and the non-working population. A dependency ratio of 60 means that for every 100 people in the economically active population there are 60 people dependent on them. The dependency ratio in developed countries is usually between 50 and 75 with the elderly forming an increasingly high proportion of dependants. In contrast, developing countries typically have higher dependency ratios, which may reach over 100. Here young people make up the majority of dependants. The dependency ratio is important because the economically active population will in general contribute more to the economy. In contrast, the dependent population tend to be bigger recipients of government funding, particularly for education, health care and public pensions.
Elderly dependency ratio is the ratio of the number of people aged 65 and over to those 15–64 years of age.
number aged over 64 number aged 15–64)
× 100
Youth dependency ratio is the ratio of the number of people aged 0–14 to those 15–64 years of age.
number aged 0–14 number aged 15–64
Now test yourself 5 6 7 8 9
× 100
× 100
Tested
Define infant mortality rate. Briefly describe the contrast in the causes of death between more developed and less developed countries. What do you understand by the terms (a) population structure and (b) population pyramid? What does a dependency ratio of 80 mean? How does the structure of dependency vary between developed and developing countries?
Answers on p.215
4.2 Demographic transition The demographic transition model Although the birth and death rates of no two countries have changed in exactly the same way, some broad generalisations can be made about population change that are illustrated by the model of demographic transition (Figure 4.4).
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Revised
Demographic transition is the historical shift of birth and death rates from high to low levels in a population.
Cambridge International AS and A Level Geography Revision Guide
