Middle class families in the most prosperous regions in China are finding the least happiness in life because of the high stress of daily life, a survey has found.

Despite good health, better education and higher incomes, the middle class is discovering that economic pressures and little time to spend with family members are major sources of annoyance, according to a recent survey by insurance company Manulife-Sinochem.

"The middle class is a 'sandwiched class', being worse off than some and better off than many," said Yan Ye, a professor with the North China Institute of Science and Technology.

"The government should expand coverage of social security, promote low-income housing projects and adjust income distribution to help them," Yan said.

Around 200 million to 300 million people belong to the middle class in China, accounting for 23 percent to 25 percent of the total population and increasing by one percent every year, Yan said.

The survey polled more than 70,000 people aged 20 to 40 in 35 cities across the country. All respondents had a yearly income above 50,000 yuan ($7,300). In 2009, the per capita GNP of China was $3,678.

The survey results reveal that those with annual household incomes from 110,000 yuan to 200,000 yuan were the happiest. People aged 30 to 35 years old are generally happier than other age groups. And those living in second tier cities experience more happiness than those in large cities such as Beijing, Shanghai and Shenzhen.

Residents of Jiangsu, Sichuan, Fujian and Chongqing rank tops in terms of happiness, with about 50 percent of people satisfied with their present situation.

"Fifty thousand yuan a year might be good money for someone in a second-tier city. But that is not so in Beijing," says Jian Biao, a 23-year-old Beijinger.

According to Yan, people usually have a higher expectation of income in big cities. So they are more likely to lack a sense of security and to feel injustice.

According to the survey, the major pressures of living in a big city lie in roaring housing prices, competition at work, traffic congestion and increasing education costs.

"As people become wealthier, they start to pursue a better quality of life. The transition from focusing on careers to the quality of life will bring about problems that disappoint people," Liu Jun, a professor with Shenzhen University, was quoted by Guangzhou Daily.