Define crude birth rate and crude death rate and explain why age adjustment is sometimes necessary.

• A. CBR = births per 1,000 population; CDR = deaths per 1,000; age adjustment accounts for age distribution differences to compare populations fairly.
• B. CBR = births per 100; CDR = deaths per 100; age adjustment concerns sex distribution.
• C. CBR = births per 1,000; CDR = deaths per 10,000; age adjustment is never needed.
• D. CBR = births per 10,000; CDR = deaths per 10,000; age adjustment uses median age.

Answer: (A)

Crude birth rate and crude death rate express births and deaths in a population relative to its size, both measured per 1,000 people. The crude birth rate is the number of live births in a year divided by the mid-year population, times 1,000. The crude death rate is the number of deaths in that year divided by the mid-year population, times 1,000. Age adjustment is sometimes necessary because a population’s age structure strongly influences these rates. If one population has more people in reproductive ages, its birth rate will tend to be higher even if underlying fertility is similar; if another has more elderly people, its death rate may appear higher. Adjusting to a standard age distribution removes the effect of differing age structures, allowing fair comparisons of fertility or mortality across populations. The option that correctly states births and deaths per 1,000 and notes that age adjustment accounts for age distribution differences to compare populations fairly is the best fit.