The 2009 Global Trends report reviews statistical trends and patterns in populations considered to be of concern to the United Nations High Commissioner for Refugees (UNHCR). This can include refugees, returnees, stateless persons and certain internally displaced persons (IDPs) - collectively referred to as "persons of concern". In doing so, the report describes some of the major humanitarian developments that occurred in 2009, many of them leading to involuntary movements of millions of people, both within and across borders.