2.3 Population Composition

What is a Population Composition?

Population composition refers to the characteristics of a population. This can be age, gender, race, and occupation. Population composition is important when determining the needs of a population. For example, a population with a high proportion of elderly people would have different healthcare needs than a population with a high proportion of young people. Policymakers and organizations use the population composition of the area to make informed decisions about how to distribute and allocate resources to the population, and how to address the needs of the population.

Sex Ratio

The sex ratio is the number of males per one hundred females in the population. That and age structure are analyzed and mapped in regions around the world. In the developed world there are more women than men. 

This is because life expectancy is longer for women than men in every country. This is because men tend to have jobs with higher mortality rates (construction, police, military). Men are at higher risk of heart disease. 

Men also die in accidents more often. 

In the developing world, there are more men because male babies are preferred. In India, it is illegal to find out the sex of the baby in utero, because of so many abortions of female fetuses. In China, there are now millions more men than women in their childbearing years, because during the one-child policy male babies were strongly preferred.

➕ China's woman shortage creates an international problem 

➕ Indian police raid illegal ultrasound centers to save unborn girls

Age Structure

Patterns of people at various ages vary in different regions within countries. Cities with large universities have an inordinate number of people aged 15-24. Parts of Florida and Arizona with large retirement communities have a high percentage of people 60 and older. 

In some countries, you will find an extremely high number of men between their 20s and 50s, because of so many migrant workers coming in for employment opportunities.

Different types of age structures:

• Youthful:  high proportion of people in younger age groups, small number of elderly people- high fertility rates, high dependency ratio- developing countries in Africa and Asia
• Aging: large proportion of elderly people, relatively small number of young people- low fertility rates, high dependency ratio- Japan, Italy, Germany
• Maturing: large number of people in the middle age groups, decreasing number of people in younger and older age groups- moderate fertility rates, moderate dependency ratio- China, South Korea, Brazil
• Declining: decreasing number of people in all age groups- low fertility rates, low dependency ratio- Bulgaria, Latvia, Ukraine

Population Pyramids

The most important tool in measuring sex ratio and age structure is the population pyramid, which is a bar graph that represents the distribution of the population by sex and age. Population pyramids use five-year increments of age and separate males on the left and females on the right (women are always right!) 

This can show you if there is a high or low dependency ratio, more females or males, or a high percentage of young or old. 

What can you learn from population pyramids?

1. Dependency ratio: number of people who are not of working age (too young or too old) relative to the number of people who are of working age
2. Fertility rate: Showing the proportion of the population that is in the child-bearing ages
3. Mortality rates: Compares the sizes of the different age groups over time
4. Gender Balance: Ration of males to females in a population
5. Population Projections: Make projections about the future size and age structure of a population
6. Population growth: Compare the size of different age groups

This is very handy when analyzing a country’s stage in the demographic transition model (DTM). It is the process of change in a society’s population from a condition of high crude birth and crude death rates, and low rates of natural increase, to a condition of low crude birth and crude death rates, low rate of natural increase, and higher total population.

Demographic Transition Model (DTM)

The DTM is a theory that explains how a population changes over time. This model consists of 4 stages (although a fifth stage is being considered).

• Stage 1: Pre-industrial society: high birth rates, high death rates, the population grows slowly or is stable

• State 2: Early industrialization: birth rates remain high, death rates decline (due to improvements in healthcare and living conditions), and the population grows at a rapid pace

• Stage 3: Late industrialization: birth rates decline (due to changes in social norms and increased access to education and contraception), and the population grows at a slower rate

• Stage 4: Post-industrial society: low birth rates, low death rates, and the population grows slowly or is stable

🎥 Watch: AP HUG - Population Pyramids