"Though estimates vary widely, approximately 900,000 North Koreans, or 10 percent of North Korea's population, migrated to the South between 1945 and 1953. This period is divided into two parts: liberation after Japanese colonialism (August 15, 1945 to June 25, 1950) and the Korean War (June 25, 1950 to July 27, 1953). The 900,000 estimate does not include South Koreans who returned to the South from North Korea or Manchuria during the liberation period, or POWs who moved following the armistice agreement."
Economic, social, and political conditions have pushed North Koreans to illegally leave their country and migrate to South Korea, China, Russia, and elsewhere. MPI's Hiroyuki Tanaka examines humanitarian and economic migration flows from North Korea, and the situation of North Koreans living abroad.
www.migrationpolicy.org
I lived in Korea, had some of its History knocked into me, surprising what sticks in your head after decades. Makes it easier to google things I think I remember. :)
"The Democratic People's Republic of Korea, or the DPRK, adheres to a strict Stalinist pattern of zero tolerance towards overseas migration. However, after the Korean War, North Korean defectors began to try and escape to South Korea in search of a better life. Before the start of the Korean War, the number of migrators between the North and the South was between 456,000 and 829,000. Through the years 1950-1953, an estimated 400,000-650,000 people migrated. Between 1945-1953, about 10 percent of the population left the North, but these numbers dramatically decreased after the war was over.[6]"