Natural Population Change is calculated by
- (a)subtracting the death rate from the birth rate
- (b)multiplying the death rate with the birth rate
- (c)adding the death rate with the birth rate
- (d)subtracting the birth rate from the death rate
Correct — A, subtracting the death rate from the birth rate. Natural population change counts only births and deaths, leaving migration out. Subtracting the crude death rate from the crude birth rate gives the rate of natural increase, and where deaths outnumber births the figure turns negative, which is natural decrease. Adding migration to this gives the total change in a population.
- (b)multiplying the death rate with the birth rate — Multiplying two rates produces a quantity with no demographic meaning. The two are measured on the same scale, per thousand of population, precisely so that they can be subtracted.
- (c)adding the death rate with the birth rate — Adding them would make a population with high births and high deaths look fast-growing, when in fact such a population may hardly grow at all — which is exactly the first stage of the demographic transition.
- (d)subtracting the birth rate from the death rate — This reverses the subtraction and flips the sign. It would report a growing population as shrinking.
The crude birth rate is live births per thousand people in a year and the crude death rate is deaths on the same basis. Their difference is the rate of natural increase, usually expressed per thousand or as a percentage. Total population change adds net migration to that difference, which is why a city can grow rapidly while its natural increase is small.
The demographic transition model is where this arithmetic earns its keep. In the first stage both rates are high and natural increase is small; in the second the death rate falls sharply while births stay high, and natural increase peaks; in the third births fall too and growth slows again. India's crude birth rate has fallen well below twenty per thousand while the death rate sits far lower still, so natural increase continues but is narrowing, and the country's total fertility rate has fallen to around replacement level.
- Natural population change is the crude birth rate minus the crude death rate.
- Both rates are expressed per thousand of the population per year, which is what allows the subtraction.
- Total population change is natural change plus net migration.
- Where the death rate exceeds the birth rate the result is negative, which is natural decrease.
- Natural increase is largest in the second stage of the demographic transition, when death rates have fallen but birth rates have not.
Keeping the two lines apart is what separates a country whose population grows from within from one that grows because people move in.
- Adding the two rates instead of subtracting them.
- Reversing the subtraction and reporting growth as decline.
- Treating natural change as the whole of population change and forgetting migration.
A definition item on a demographic formula. Every wrong option is a different operation on the same two numbers, so the arithmetic has to be remembered exactly.
The total fertility rate in an economy is defined as :
- (a) the number of children born per 1000 people in the population in a year
- (b) the number of children born to a couple in their lifetime in a given population
- (c) the birth rate minus death rate
- (d) the average number of live births a woman would have by the end of her child-bearing age
Answer(d) the average number of live births a woman would have by the end of her child-bearing age
Prelims put this very formula among the options as a distractor. Recognising that birth rate minus death rate is the natural growth rate, and not the total fertility rate, is what settles both questions.
Consider the following specific stages of demographic transition associated with economic development: 1. Low birthrate with low death rate 2. High birthrate with high death rate 3. High birthrate with low death rate Select the correct order of the above stages using the codes given below:
- (a) 1, 2, 3
- (b) 2, 1, 3
- (c) 2, 3, 1
- (d) 3, 2, 1
Answer(c) 2, 3, 1
Where the subtraction becomes a model. Ordering the stages of the demographic transition is an exercise in tracking how the gap between the two rates opens and then closes.
- practice — not a real PYQ
A country has a crude birth rate of 22 per thousand and a crude death rate of 7 per thousand. Its rate of natural increase is
- (a)29 per thousand
- (b)15 per thousand
- (c)1.54 per thousand
- (d)154 per thousand
Answer(b) 15 per thousand — 22 minus 7, which is a natural increase of 1.5 per cent a year.
- practice — not a real PYQ
In which stage of the demographic transition is the rate of natural increase highest?
- (a)High birth rate with high death rate
- (b)High birth rate with falling death rate
- (c)Low birth rate with low death rate
- (d)Falling birth rate with rising death rate
Answer(b) High birth rate with falling death rate — the gap between the two rates is at its widest in this stage.