Which of the following statements best explains why age-specific rates are used in demography?

Correct — B. Fertility and mortality change sharply with age. Births come from women of about 15–49, and the risk of death is highest in infancy and old age.

A crude rate divides events by the whole population and hides this. An age-specific rate divides the births or deaths in one age group by the population of that group, so it shows the age-wise variation: option (b).

Why the others are wrong

• (a)
  They help identify regional literacy levels — Age-specific rates count births and deaths by age. Literacy is a separate indicator, measured by the literacy rate.
• (c)
  They show the economic condition of elderly people — They cover every age group, not just the elderly, and they count births or deaths, not economic condition.
• (d)
  They reduce the total number of indicators needed — They add indicators, one rate per age group, rather than reduce them. A single total fertility rate is built by summing them.

An age-specific fertility rate (ASFR) is the number of births in a year to women of one age group divided by the number of women in that group. Age-specific death rates are built the same way.

Adding the five-year ASFRs from 15–19 to 45–49 and multiplying by 5 gives the total fertility rate (TFR): the children a woman would have over her life at current rates.

Because each rate compares like with like, populations with different age structures can be compared fairly.

Key facts

• ASFR = births to women in an age group ÷ women in that age group.
• TFR = 5 × the sum of the five-year ASFRs from ages 15–19 to 45–49.
• Crude birth and death rates are per 1,000 of the whole population, so they depend on its age structure.

Common traps

• Choosing (d) because one TFR figure looks simpler, when it is built from many age-specific rates.
• Confusing age-specific rates with the age–sex pyramid, which shows population, not births or deaths.

No directly related past PYQ was found.