They may be richer but China's rapidly expanding band of mega-wealthy entrepreneurs are apparently finding that their economic success is not bringing them the happiness they might have expected.

Many of their problems can be linked back to stress, according to a new survey, with around 80 percent of the chief executives polled saying they felt "substantial or increased pressure'' over the past five years.

The direct result of that was a decrease in happiness at home, says the China Entrepreneur Survey System (CESS), which has been producing a yearly study of the country's entrepreneurs since 1993.

The report claimed those working in the pharmacy, chemical fibre, steel and auto industries felt the most stress, while those in the likes of plastics and beauty products felt less stress.

The CESS survey works via a "happiness index'' which raises a number of questions about the subject's well-being and asks them to rate their response on a scale between zero and five - five being "happy'' and zero being pretty close to miserable.

This year the overall average was 3.64, a decline from 3.76. The lowest mark ever recorded in the survey was 3.60 in 2008 - just after the global financial crisis emerged. Overall, the survey found that China's female entrepreneurs were happier than their male counterparts.

Forbes magazine earlier this year reported that China is now second only to the United States in term of the numbers of billionaires it has. The US has 403 and China 64 and there are 1,011 worldwide.

China's annual Hurun report - which charts the nation's wealthy - also claimed this year there were 825,000 people with a net worth of more than 10 million yuan (1.1 million euro) in the country, and 51,000 who held more than 100 million yuan (11.5 million euro) each.