Q.What is infant mortality rate?

The Demographic Transition: From High Births and Deaths to Low Ones

Imagine a village a hundred years ago. Families have many children — six, seven, eight — because many babies don't survive infancy, and children are needed to work on the farm. Disease is common, and life expectancy is low. Now imagine that same village today. Families have one or two children. Almost every child survives. People live into their seventies and eighties. How did we get from one world to the other?

That journey is what the Demographic Transition Theory describes. It is a model that explains how a country's population changes as it develops from a pre-industrial, agrarian society to a modern, industrial one. It is not a law of nature, but a pattern observed across many countries.

The theory tracks two key rates:

• Birth rate (BR): Number of live births per 1,000 people per year.
• Death rate (DR): Number of deaths per 1,000 people per year.

The difference between them gives the natural growth rate of the population (ignoring migration).

The transition is divided into five stages. Let's walk through them.

Stage 1: High Stationary (Pre-Industrial Society)

Both birth rate and death rate are high and roughly equal. The population is stable — it grows very slowly, if at all, and is kept in check by famine, disease, and poor healthcare.

Why are birth rates high? No family planning, children as economic assets, high infant mortality (so you have many to ensure some survive), and social/religious norms favouring large families.

Why are death rates high? Poor sanitation, limited medical knowledge, frequent epidemics, and periodic famines.

The result: a young population, but one that barely grows.

Stage 2: Early Expanding (The Mortality Revolution)

This is where the drama begins. Death rate falls sharply, but birth rate remains high. The gap between the two widens, and the population begins to grow rapidly.

Why does the death rate fall? Improvements in food supply (better agriculture, transport), sanitation (clean water, sewage), and public health (vaccinations, basic medicine). These changes often come from outside — new technology or colonial administration — and can happen quickly.

Birth rates stay high because family size is still driven by old habits and norms. People don't immediately change their behaviour just because fewer children are dying.

Example: India entered Stage 2 around the 1920s–1940s, when death rates began to fall due to better public health, but birth rates remained high until the 1970s.

Stage 3: Late Expanding (The Fertility Transition)

Now birth rate begins to fall, following the death rate down. The population still grows, but at a decreasing rate.

Why does the birth rate finally fall? Several factors work together:

• Urbanisation: children become an expense, not an asset (no farm work, need schooling).
• Women's education and employment: later marriage, smaller families.
• Availability of contraception.
• Decline in infant mortality: parents no longer need to have many children to ensure some survive.
• Social change: the ideal family size shrinks.

The death rate continues to fall slowly, but the birth rate falls faster. The gap narrows.

Stage 4: Low Stationary (Modern Industrial Society)

Both birth rate and death rate are low and roughly equal. The population is stable again, but at a much larger size than in Stage 1. Life expectancy is high, family size is small (often around replacement level — about 2.1 children per woman).

Most developed countries (USA, UK, Japan, much of Europe) are in Stage 4.

Stage 5: Declining (The Ageing Society)

This is a more recent observation. Birth rate falls below death rate, so the population begins to shrink naturally (ignoring immigration). The population is also very old. …