Population

A country's population size changes due to two main factors: natural change and migration. Natural change is the difference between the number of live births and the number of deaths. Migration is the movement of people into or out of a country. When more people are born than die, the population grows naturally. When more people move into a country (immigrate) than leave (emigrate), the population also grows. The overall change is a combination of both these factors.

Population structure refers to the composition of a population, usually broken down by age and sex. This is most clearly shown using a population pyramid. A population pyramid is a special type of bar chart. Age groups are shown on the vertical axis, and the percentage or number of people in each group is on the horizontal axis. Males are shown on the left and females on the right. The shape of the pyramid tells a story about a country's population. A wide base indicates a high birth rate and a youthful population. A narrow base and wider top indicate a low birth rate and an ageing population.

The dependency ratio is a key economic measure that compares the size of the dependent population to the size of the working-age population. The dependent population consists of those who are generally not in the workforce: children (usually under 15) and the elderly (usually over 64). The working-age population (15-64) is responsible for economically supporting the dependents. A high dependency ratio means there are more dependents for each working person to support, which can strain government finances (for pensions, healthcare, education) and reduce the country's potential for saving and investment.

Developed and developing countries show very different population trends. Developed countries (e.g., Germany, Japan) typically have low birth rates, low death rates, and high life expectancy. This results in slow, zero, or even negative population growth and an ageing population structure. Reasons include high costs of raising children, high status and education levels for women, and strong pension systems. In contrast, many developing countries (e.g., Nigeria, Pakistan) have historically high birth rates, although these are often falling. Death rates have fallen sharply due to better healthcare and sanitation. This combination leads to rapid population growth and a youthful population structure. Reasons for higher birth rates include cultural norms, a lack of access to contraception, and children being seen as an economic asset or security in old age.

Changes in a population's size and structure have significant economic consequences. An ageing population, common in developed countries, leads to a smaller workforce, potential skills shortages, and slower economic growth. It also increases government spending on pensions and healthcare, which may require higher taxes on the smaller working population. A youthful population, common in developing countries, creates a high 'youth dependency ratio', straining education and health services. However, if these young people can be educated and employed, it can lead to a 'demographic dividend'—a period of accelerated economic growth. Finally, overpopulation occurs when a population is too large for the available resources to maintain a reasonable standard of living, leading to problems like poverty, unemployment, and environmental degradation.

The structure of a population can also be analysed by its occupational and geographical distribution. Occupational distribution refers to how the workforce is spread across the three main economic sectors: Primary (extracting raw materials, e.g., farming, mining), Secondary (manufacturing and construction), and Tertiary (providing services, e.g., banking, teaching). As an economy develops, its occupational structure changes. The workforce moves from being dominated by the primary sector, to the secondary, and finally to the tertiary sector. Geographical distribution describes where people live within a country. A major trend linked to economic development is urbanisation—the increasing proportion of the population living in towns and cities, often as people move from rural areas in search of work.