Key population metrics and calculations

Population metrics help measure changes in a country's population size and structure over time. These include rates related to births, deaths, and migration, which are essential for understanding economic and social trends.

Main population metrics

• Birth rate - This is the number of live births per thousand of the population in one year, calculated by dividing the number of live births by the population and multiplying by 1000. The crude birth rate is a basic measure of births that does not account for details like the age of those giving birth.
• Death rate - This is the number of deaths per thousand of the population in one year.
• Natural increase in population - This happens when the birth rate is higher than the death rate, leading to population growth without considering migration.
• Net immigration (or positive net migration) - This occurs when the number of people entering a country (immigration) is greater than the number leaving (emigration).

Calculating net migration

Net migration shows the overall change in population due to people moving in and out of a country. It is often given as a rate per thousand of the population.

$\text{Net migration}=(\text{population}÷1000)\times \text{net migration rate}$

Where:

• Population = Total number of people in the country
• Net migration rate = Rate per thousand (positive for net immigration, negative for net emigration)

A positive result means more people are entering than leaving, contributing to population growth.

Worked example - Calculating net migration

A country has a population of 75 million and a net migration rate of 4 per thousand. Calculate the net change in population due to migration.

Step 1: Identify the values

• Population = 75,000,000
• Net migration rate = 4

Step 2: Apply the formula

$\text{Net migration}=(\mathrm{75,000,000}÷1000)\times 4$

Step 3: Perform the calculation

$\text{Net migration}=\mathrm{75,000}\times 4=\mathrm{300,000}$

This means 300,000 more people enter the country than leave.

Factors influencing population growth in developing and developed countries

Population growth patterns vary with a country's level of economic development. In general, as countries become more developed, population growth slows down because death rates fall first, followed by a sharper decline in birth rates.

Factors extending life expectancy and reducing death rates

These improvements often occur as countries develop, leading to longer lives and lower death rates:

• Better healthcare systems and access to medical treatments.
• Improved education, which promotes healthier lifestyles.
• Enhanced sanitation and clean water supplies.
• Upgraded housing conditions that reduce disease risks.
• Better nutrition from reliable food supplies.

Factors reducing birth rates

Birth rates tend to fall in developed countries due to social and economic changes:

• Lower infant mortality, meaning families need fewer children to ensure some survive.
• Higher costs of raising children, including education and childcare.
• Greater participation of women in the workforce, delaying or limiting family size.

Population growth in less developed countries

Less developed countries often experience high population growth for several reasons:

• Children are needed to support elderly family members in the absence of formal pension systems.
• Limited access to birth control and family planning services.
• Lower costs associated with raising children in rural or subsistence economies.
• Restricted education for women, which can lead to larger families.
• High infant mortality rates, prompting families to have more children to compensate.

Population growth in highly developed countries

In highly developed countries, the birth rate may fall below the death rate, causing a natural population decrease. However, overall population can still grow due to net immigration, as people move from less developed regions seeking higher wages and better living conditions.

Impacts of population structures on economies

The age structure of a population affects dependency ratios and creates specific economic challenges. High birth rates in developing areas lead to youthful populations, while developed regions often deal with aging populations.

Effects of high birth rates in developing regions

• Populations with a low average age.
• High youth dependency ratios, where a large number of young people rely on a smaller working-age group for support.
• This can strain resources like education and healthcare.

Challenges of aging populations in developed regions

• High elderly dependency ratios, with more retirees depending on fewer workers.
• Increased costs for healthcare due to age-related needs.
• Greater burdens on pension systems, as more people draw benefits for longer periods.
• Governments may respond by raising the retirement age to reduce pension costs and keep more people in the workforce.

The concept of optimum population

The optimum population is a theoretical point where a country's population size maximises economic efficiency. It balances population with available resources and technology to achieve the highest output per person.

Key aspects of optimum population

• Optimum population - This exists when output per head is at its maximum, given the current levels of other factors of production (like land and capital) and existing technical knowledge.

• Underpopulated - This describes when the population is below the optimum level, leading to potential for increasing returns if more people are added.

• Overpopulated - This describes when the population exceeds the optimum level, resulting in decreasing returns and inefficiencies.

The concept is dynamic, as changes in technology or resource availability can shift what is considered optimum over time.

Patterns of rural-urban migration

Migration between rural and urban areas varies by development level and can impact infrastructure and economic growth.

Migration in less developed regions

• Higher proportions of the population live in rural areas.
• Rapid rural-urban migration occurs as people seek better opportunities in cities.
• This creates pressure on urban infrastructure, such as housing, transport, and services.

Migration in highly developed regions

• Populations are predominantly urban, with minimal rural-urban migration.
• Some areas see urban-to-rural migration, enabled by technology that allows remote working and reduces the need to live in cities.