Definition: Birth rate is the demographic measure of the rate at which children are born. The most well known is the crude birth rate, which is the number of births that occur each year per 1,000 people in the midyear population. It is called “crude” because it does not take into account the possible effects of age structure. If a population has an unusually large or small number of women in childbearing age, then the crude birth rate will tend to be relatively high or low regardless of the actual number of children a woman has. For this reason, age adjusted birth rates are preferred for making comparisons, either over time or between populations.