Siheung's 2021 population is now estimated at 442,790. In 1950, the population of Siheung was 1,571. Siheung has grown by 2,409 since 2015, which represents a 0.55% annual change. These population estimates and projections come from the latest revision of the UN World Urbanization Prospects. These estimates represent the Urban agglomeration of Siheung, which typically includes Siheung's population in addition to adjacent suburban areas.