Residents and migrant workers are fleeing big China cities - resulting in reverse migration.

High costs of living, an aging population and the popularity of working online have contributed to the reversal of the former rush to big cities - which had defined China's economic expansion over the past decades.

China's statistics agency said millions didn't travel back to cities after the coronavirus pandemic last year. The statistics bureau data showed 2.46 million fewer migrant workers in big cities as of the end of March compared with the same period in 2019.

Economists at Hang Seng China said rural-urban migration had already slowed even before the pandemic hit. The trend is expected to continue as technologies and new working opportunities such as livestreaming e-commerce become more popular. Economists said the rising cost of living in big cities was a factor in people deciding to stay at home.

"Rural-urban migration already slowed before Covid-19 and had its first decline in 2020. Reverse migration will pick up pace in coming years, partly because (workers) can't afford city housing and don't have access to city health care," Dan Wang, chief economist at Hang Seng China, said.

Wang said another contributing factor to reverse migration was the country's aging population. She said migrant workers aged 50 and older had more than doubled in the past decade to 26%.

Government policies may have contributed to the trend, economists said. China's economy boomed after the state loosened its grip on the economy over the past few decades. Millions of people from provinces flocked to large cities such as Beijing and Shenzhen to look for jobs.

As a result of an influx of migrants, some cities imposed residency restrictions, which prevented some workers from getting their children into schools, renting homes and using public health care. Some cities evicted migrants.