Population transfer or resettlement is the movement of a large group of people from one region to another, often a form of forced migration imposed by state policy or international authority and most frequently on the basis of ethnicity or religion. Banishment or exile is a similar process, but is forcibly applied to individuals and groups. Population exchange is in theory at least the (presumably non-forcible) transfer of two populations in opposite directions at about the same time; but the reality of the effects of these exchanges has always been unequal, and at least one half of the so-called "exchange" has usually been forced by the stronger or richer participant. Such exchanges have taken place several times in the 20th century: two examples are the traumatic partition of India and Pakistan and the mass expulsion of Anatolian Greeks and Greek Muslims from Turkey and Greece, respectively, during their so-called Greek-Turkish population exchange, involving approximately 1.3 million Anatolian Greeks and 354,000 Greek Muslims, most of whom were forcibly made refugees and de jure denaturalized from their homelands.