Demographics (Economics)

Demographics, in economics, is the study of the size, composition and change of a population, and of how those features affect the economy. The main variables are fertility (births), mortality (deaths and life expectancy) and migration, which together determine how many people there are, how old they are and where they live. These in turn shape the supply of labor, patterns of consumption and saving, demand for housing and services, and the cost of pensions and health care.

Demography as a scientific discipline is older than modern economics, but the two overlap closely. Economists use demographic data from censuses, civil registration and surveys, and projections from bodies such as the United Nations Population Division. Demographic change is slow and fairly predictable over decades, which makes it a key input into long-term forecasts of growth, government spending and the dependency ratio.

Think of a country's population as a long queue moving slowly forward through life. People join at birth, move through school, working years and retirement, and leave at death, while migrants join or leave partway along. If many people joined the queue in one period, that bulge moves along it for decades.

Economists watch where the bulges are. A bulge of young adults means plenty of workers and strong demand for first homes. A bulge of retirees means more spending on pensions and care and fewer new workers. Because the bulges move slowly, their economic effects can be seen coming years in advance, even if policy is slow to respond.

Population change follows a simple accounting identity, sometimes called the demographic balancing equation:

• $P_t$ and $P_{t+1}$ are the population at the start and end of the period.
• $B$ and $D$ are births and deaths; their difference is the natural increase.
• $I$ and $E$ are immigrants and emigrants; their difference is net migration.

Example: a country starts the year with 50 million people, records 500,000 births and 450,000 deaths, and has 200,000 immigrants and 100,000 emigrants. Its population at year end is $50{,}000{,}000 + 500{,}000 - 450{,}000 + 200{,}000 - 100{,}000 = 50{,}150{,}000$, growth of 0.3%, two-thirds of it from migration.

The key fertility measure is the total fertility rate, the average number of children a woman would have over her lifetime at current rates. About 2.1 is needed to replace each generation in countries with low child mortality. Many countries are now far below that; South Korea's rate was about 0.7 in 2023, among the lowest ever recorded nationally.

The United Nations' World Population Prospects 2024 estimated the world population at about 8.2 billion in 2024 and projected a peak of around 10.3 billion in the mid-2080s, followed by a slight decline. It found that 63 countries and areas, including China, Germany, Japan and Russia, had already passed their population peak, and projected that by the late 2070s people aged 65 and over would outnumber children under 18. India overtook China as the most populous country in 2023, according to UN estimates. Most future growth is expected in sub-Saharan Africa and parts of Asia, including Pakistan.

These trends reflect the "demographic transition", a pattern first described in the early twentieth century: as countries develop, death rates fall first, causing rapid growth, then birth rates fall, and growth slows. Thomas Malthus had argued in 1798 that population would tend to outrun food supply; the rise in agricultural and general productivity since then has so far proved that fear wrong at a global level.

Demographic change affects economies through several channels:

• Labor supply and growth. Growth in GDP equals growth in hours worked plus growth in output per hour. A shrinking working-age population drags on the first, putting more weight on human capital and technology.
• The demographic dividend. When fertility falls, the working-age share rises for a few decades, which can boost growth if there are jobs and investment, as in much of East Asia from the 1960s.
• Saving and interest rates. Under the life-cycle hypothesis, middle-aged populations save more and retirees dissave. Some economists link high saving by ageing baby boomers to low real interest rates and stagnation in rich countries.
• Inflation. Charles Goodhart and Manoj Pradhan argued in 2020 that ageing and slower labor-force growth would raise wages and inflation over time; others expect ageing to keep inflation and interest rates low. The question is unresolved.
• Public finances. Ageing raises spending on pensions, social security and health, pressing on fiscal policy and the national debt.

Migration is the fastest-moving demographic variable and the most politically contested. For receiving countries, migrant workers can ease labor shortages and slow population ageing; debates focus on effects on wages of low-paid residents, public services and integration, where research generally finds small average wage effects but disagreement persists. For sending countries, emigration can mean a loss of skilled workers but also brings remittances, which are a major source of foreign currency in Pakistan, India, the Philippines and many other developing countries. Emerging markets with young populations face the opposite challenge from ageing ones: creating enough jobs for large numbers of new entrants, many of whom end up in the informal economy.

• United Nations: World Population Prospects
• World Bank: Population