The survey of about 7,000 expats in 37 countries showed that Asia has widened its appeal for expatriates, offering higher average salaries than anywhere else. Expats in Asia made US$74,000 (HK$574,000) on average last year, compared to $64,000 elsewhere, the bank said.

The decision by expats to move to China is still mainly driven by economic factors, the survey showed. Seven in ten expats moved to the mainland because of better job opportunities, whereas only four in ten emigrated to Hong Kong to move up the career ladder.

In terms of quality of life, the mainland beat the SAR this year in almost every category in the survey, including disposable income, diet, commute, accommodation and the weather. While the mainland ranked second after Brazil in terms of ease of integration, Hong Kong stood at a low 28th rank globally.

However, Hong Kong still beat the mainland on core matters of childcare, healthcare, entertainment and work culture.

Almost half, 49 per cent, of the expats surveyed living in the mainland said they enjoyed a better work-life balance than in their home country. Despite frequent reports about hazardous air pollution, 45 per cent of expats said life in the PRC has made them more active in sports.

The large majority of expats in the mainland, 86 per cent, made an effort to learn the local language in China, in contrast to 60 per cent of those expats living elsewhere, according to the survey.

Hong Kong still stood out as an attractive destination for families, ranking eleventh globally. Almost six in ten said childcare in the SAR was better than in their home countries, and slightly more than five in ten said education was better in Hong Kong. Germany, Singapore and France were ahead of the SAR in terms of the best places to raise a family.

One reason for the increased appeal of the mainland over Hong Kong could be the comparatively inexpensive cost of living. According to a study earlier this year by the Economist Intelligence Unit, life in Hong Kong was more expensive than in all major Chinese cities.

However, a study of compensation packages for expats by the human resources firm ECA International later in the year found that Hong Kong was ranked as cheaper to live in than Beijing and Shanghai.

An HSBC spokesperson dismissed criticism over the sample sizes, saying those in China and Hong Kong considerably exceeded their minimum sample of thirty. Because of changes in methology, the company refrained from making year-on-year comparisons, she said.

Commenting on a wider trend, the spokesperson said expat wealth has been gradually heading east over the last six years.

"This year, Asia not only emerged as the expat social hub with 35 per cent agreeing that they enjoy a more active social life since relocating, compared with the global average of 26 per cent - the highest out of any region, Asia is also home to among the highest paid expats in the world," she wrote in an emailed statement.