It said Hong Kong would be home to 737,716 millionaires by 2028, a 17 per cent increase on 629,155 last year.

Singapore is projected to have a 13 per cent increase in the number of US dollar millionaires, going from 333,204 to 375,725, over the same period.

The report explained wealth inequality was measured by the Gini index on a scale of zero to 100. It added the definition of wealth included financial and real assets owned by households, minus debts.

The Post understands that it was calculated using wealth distribution data and did not take income distribution into account.

The index for Hong Kong dropped by 5.9 per cent from 66 in 2008 to 63 last year and that for Singapore went up 22.9 per cent from 57 to 70.

But the UBS report said the difference did not mean Singaporeans were necessarily “worse off than their peers in Hong Kong”.

Professor Wong Yu-cheung of Saint Francis University’s school of social sciences said: “The drop in property prices [in Hong Kong] could have contributed to the [improving] inequality rate.”

Wong added that the trend could also be explained by a lower number of high-income individuals in Hong Kong between 2008 and 2023, caused by people who had sold assets and left the city, or by those who had suffered a decline in earnings.

Simon Lee Siu-Po, an economist and an honorary fellow at the Asia-Pacific Institute of Business at the Chinese University of Hong Kong, said the increase in Singapore’s wealth inequality figure could have been caused by the transfer of capital from Hong Kong to the city state after 2019, as the international community monitored court cases related to the national security law Beijing-imposed in 2020.

“People can gradually see the effects of the implementation – and if I feel uncertain about something, I might diversify,” he said.

“From a macro perspective, some might feel that Hong Kong is increasingly like a city in mainland China.”

Lee added potential investors in Hong Kong might ask why they were paying a premium to put their money in the city.

He said that an influx of lower-income labour from Southeast Asia to Singapore could also have contributed to an increase in the city state’s wealth inequality, as they would be in poorer-paid positions.

The UBS report said inequality in North America had slightly decreased since 2008, but went up in Latin America, as well as in most of Eastern Europe and Asia, except for Hong Kong and South Korea.

The US ranked first for US dollar millionaires followed by mainland China, the UBS report said, based on figures from financial services giant PwC and financial media specialist Forbes.

Lee attributed Hong Kong’s predicted surge in the number of US dollar millionaires to the transfer of high-net-worth individuals and money from mainland China.

He added that the forecast could also be based on the assumption that the property market would have recovered by 2028 and that it would generate wealth for people in Hong Kong.

Sze Lai-shan, the deputy director of the Society for Community Organisation NGO, said the earnings of lower-income groups in the city lagged behind the median level by a long way, unlike other developed economies.

She said that was one of the most important gaps to bridge, especially in a climate of high interest rates.

The Gini coefficient of all households in Hong Kong on a scale of zero to one – based on post-tax monthly household income per head, including social benefits and governmental one-off relief measures – stood at 0.397 at the time of the 2021 census, a drop on the 0.420 recorded in 2016 and the 0.414 in 2011.