As required by the Namibian "Statistics Act" #66 of 1976, and in accordance with United Nations recommendations, a census is conducted every ten years. After Namibian independence the first Population and Housing Census was carried out in 1991, further rounds followed in 2001 and 2011. The data collection method is to count every person resident in Namibia wherever they happen to be. This is called the "de facto" method. For enumeration purposes the country is demarcated into 4,042 "enumeration areas". These areas overlap with constituency boundaries in order to get reliable data for election purposes as well.