Final answer:
The rate that measures the number of children born in relation to the size of a population is the birth rate, expressed as the number of live births per 1,000 people per year.
Step-by-step explanation:
The rate that measures how many children are being born in a country in relation to the size of its population is known as the birth rate.
The birth rate, typically expressed in terms of the number of live births per 1,000 people per year, helps sociologists and demographers understand the population growth dynamics of a region.
When the birth rate is considered alongside the mortality rate or death rate (the number of deaths per 1,000 people per year), analysts can determine the net population growth rate of a society. If the birth rate is higher than the mortality rate, the population is said to be increasing.