In 2011, Zhao Yigong launched an oral history project to document the Chinese sent-down youth movement during the Cultural Revolution. To date, Zhao Yigong and Han Meng have interviewed 478 subjects who took part in the movement. One particular group of the interview subjects was part of a wave of educated youths who "fled to Hong Kong," as refugees from the mainland. There in Hong Kong, these former educated youths sought better lives for themselves and contributed to the population surge in Hong Kong from the 1950s to the 1970s.