Population Education: Concepts and Dynamics
This section covers Population Education: Concepts and Dynamics. The exam tests demographic rates, ratios, age-sex pyramids, demographic transition and the difference between growth from natural increase and migration.
Core rules
- A census counts the population at a point in time. Vital registration records births, deaths and migration continuously.
- Crude birth rate is births per 1,000 people per year. Crude death rate is deaths per 1,000 people per year. Natural increase is birth rate minus death rate per 1,000. Population growth rate also includes net migration.
- Total fertility rate is the average number of children a woman would have over her reproductive life at current age-specific rates. Replacement level is about 2.1 in low-mortality settings.
- An age-sex pyramid with a broad base shows high fertility; a narrowing base shows fertility decline; a bulge shows a past baby boom.
- Demographic transition moves from high birth and high death rates, to high birth and falling death rates with rapid growth, to falling birth and low death rates, and finally to low birth and low death rates.
- Density is people per square kilometre. In the Indian census, sex ratio is females per 1,000 males; child sex ratio is for ages 0-6.
- Approximate doubling time is 70 divided by the annual percentage growth rate.
Worked example
A district has a birth rate of 20 and a death rate of 7 per 1,000, with negligible migration. Natural increase = 20 − 7 = 13 per 1,000, which is 1.3% per year. Doubling time is about 70 ÷ 1.3 ≈ 54 years. The reasoning is that per-1,000 rates become percentages when divided by 10, and the rule of 70 applies to percentage growth.
Traps
- Do not read 13 per 1,000 as 13%.
- Population growth is not caused by births alone; migration can add or subtract.
- TFR is not the same as crude birth rate.
- Sex ratio and literacy rate are different indicators; do not confuse them.
Odisha's 2011 Census population was about 42 million, with wide rural-urban and district differences.