The majority of squatting is residential in nature. As a phenomenon it tends to occur when a poor and homeless population makes use of derelict property or land through urban homesteading. According to a 2003 estimate by United Nations in UN-HABITAT report, there were about one billion people in squatter settlements and slums. According to an academic Kesia Reeve, "squatting is largely absent from policy and academic debate and is rarely conceptualised, as a problem, as a symptom, or as a social or housing movement."