Key Definitions | Causes | Advantages and Disadvantages

Before you dive into causes or case studies, you need to get the key definitions right:

Rate of Natural Increase – Birth rate minus death rate, without factoring in migration
Replacement Rate – The number of children needed per woman to keep population stable (usually 2.1 in developed countries)
Total Fertility Rate (TFR) – The average number of births per thousand women of childbearing age
Infant Mortality Rate – The number of babies who die before their first birthday, per 1,000 live births.

What Causes High and Low Birth Rates?

Birth rates change depending on a country’s level of development. In rural, lower-income areas, families often have more children, with kids seen as economic assets, helping with farming or earning income. Meanwhile, contraception is limited, and high infant mortality leads parents to have more births to ensure survival.

Low birth rates are more common in urban, high-income societies. Education for women improves, careers take priority, and people delay marriage and children. In many cases, fewer births reflect more freedom and gender equality, not just cost of living.

These shifts can be seen in the Demographic Transition Model, which shows how birth and death rates change as countries develop.

Pros and Cons of High vs Low Birth Rates

Whether low or high birth rates, each comes with trade-offs.

Countries with high fertility may benefit from a demographic dividend — a large, youthful workforce that can boost the economy if jobs are available. But there’s also risk of overcrowding, youth unemployment, and pressure on services.

Low birth rates ease that pressure in the short term, but they bring future challenges.

Ageing populations, labour shortages, and rising pension burdens all become national concerns. Striking the right balance is difficult — which is why so many governments are intervening.

Given the significance of how many babies you and I are having, states have at times stepped in to intervene or direct the number of children we can/ should have through birth policies.

Full Population Revision Pack available