During the generation of Japanese occupation (1910–45), some three million Koreans, mainly from the northern provinces, emigrated to Manchuria and parts of China, 700,000 to Siberia, some three million to Japan, and about 7,000 to the United States (mostly to Hawaii). From the end of World War II in 1945 through 1950, at least 1.2 million Koreans crossed the 38th parallel into the ROK, refugees either from Communism or from the Korean War. Repatriation of overseas Koreans is actively encouraged in an attempt to ameliorate the nation's chronic labor shortages. Between 1945 and 1950, an estimated 300,000 Koreans were repatriated from Manchuria and Siberia; over 93,000 out of about 600,000 Koreans in Japan were repatriated to the DPRK between December 1959 and the end of 1974. The General Association of Korean Residents in Japan actively promotes the DPRK cause, and the P'yongyang government subsidizes some Korean schools on Japanese soil. Some 250,000 people of Korean origin in Japan have links to the DPRK, providing $600–$1,800 million in annual remittances to relatives. Under a 1986 treaty with China, North Koreans apprehended as illegal immigrants in China are quickly returned to the DPRK and executed. Between 1992 and 1996, about 1,000 North Koreans fled to China, where refugees can avoid detection within large ethnic-Korean communities. Both China and South Korea have begun to construct refugee camps in anticipation of a mass exodus of the population should the North Korean government collapse. In 1999, the net migration rate was zero migrants per 1,000 population.