Fertility refers to the incidence of child-bearing in a country's population, typically measured by the number of live births within a specific period, often a year, in relation to the population size or the number of women of childbearing age. Demographers study fertility rates to understand population growth and change, as well as the social, economic, and cultural factors that influence people's decisions about having children. Factors affecting fertility rates can include levels of education and economic development, access to contraception and family planning services, cultural norms and religious beliefs about family size, the status of women in society, and government policies related to child care and parental leave. Fertility rates vary significantly across different countries and regions and have been declining in many parts of the world in recent decades.