Immigrants from mainland China are expected to be the main driver of Hong Kong’s population growth in the next three decades, according to a government document submitted to the Legislative Council.

Hong Kong’s one-way permit system had brought in 879,000 mainland Chinese since the city returned to Chinese rule in 1997, the document said, citing data from the Census and Statistics Department.

The one-way permit system allows mainlanders whose immediate families are Hong Kong permanent residents to settle in Hong Kong.

hk population
A border checkpoint in Shenzhen.

The city’s population was estimated at 7.3 million in mid-2015. This means mainland immigrants make up about 12 percent of Hong Kong’s population, excluding those who come via talent and investment entrance schemes.

The document said Hong Kong’s population was estimated to peak in 2043 at 8.22 million.

Meanwhile, cross-border couples took up nearly 40 percent of marriages registered in 2014. The government will review its population policies and continue the one-way permit system, the document said.

The legislature’s House Committee is set to hold a meeting next Monday to discuss issues relating to Hong Kong-mainland families.

Vivienne Zeng is a journalist from China with three years' experience covering Hong Kong and mainland affairs. She has an MA in journalism from the University of Hong Kong. Her work has been featured on outlets such as Al Jazeera+ and MSNBC.