The birth rate in a period is the total number of live births per 1,000 population divided by the length of the period in years. The number of live births is normally taken from a universal registration system for births; population counts from a census, and estimation through specialized demographic techniques.[clarification needed] The birth rate (along with mortality and migration rates) is used to calculate population growth. The estimated average population may be taken as the mid-year population.
The total (crude) birth rate (which includes all births)—typically indicated as births per 1,000 population—is distinguished from a set of age-specific rates (the number of births per 1,000 persons, or more usually 1,000 females, in each age group). The first known use of the term "birth rate" in English was in 1859.
The average global birth rate was 18.5 births per 1,000 total population in 2016. The death rate was 7.8 per 1,000. The RNI was thus 1.6 percent. In 2012 the average global birth rate was 19.611 according to the World Bank and 19.15 births per 1,000 total population according to the CIA, compared to 20.09 per 1,000 total population in 2007.