Child marriages have been common throughout history. They are still fairly widespread, particularly in developing countries such as parts of Africa, South Asia, Southeast Asia, West Asia, Latin America, and Oceania. Even in developed countries such as the United States legal exceptions mean that 17 US states have no minimum age requirement for marriage. The incidence of child marriage has been falling in most parts of the world. 2018 data from UNICEF showed that about 21 percent of young women worldwide (aged 20 to 24) were married as children. This is a 25 percent decrease from 10 years before. The countries with the highest observed rates of child marriages below the age of 18 were Niger, Chad, Mali, Bangladesh, Guinea, the Central African Republic, Mozambique, and Nepal with rates above 50%. Niger, Chad, Bangladesh, Mali and Ethiopia were the countries with child marriage rates greater than 20% below the age of 15, according to 2003–2009 surveys. Globally, an estimated 12 million girls annually are being married under the age of 18.