Even milk money is a heavy expenditure. They currently feed their baby an imported milk powder from Germany, and the price of the brand has been swinging upward as demand increases in tandem with falling confidence in domestic dairy products after safety-issue scandals.

Han's father had suggested bringing the child back to Xuzhou, their hometown, arguing that the grandparents can look after the baby better, and that the cost of living would be lower. The grandfather also thinks that chances in finding a good school will be better.

Han finds that decision too hard to make.

"How much money the Chinese middle class earns is much easier to measure than how happy they are," notes Zhou Xiaozheng, sociology professor at Renmin University.

"Fancy as their jobs, cars or houses may be, the pressures are enormous. They do not enjoy the benefits of the upper class, and they share the same worries of the lower classes including food safety for their children, education and the stress to succeed."

Bei Bei is single, has a Beijing hukou, three houses and fits exactly into Qian's definition of being "middle class", but the 35-year-old has her own angst.

Born and raised in Beijing, the owner of a technology company lives in a 190-square-meter house in central Beijing, and has two more she rents out. She has two cars: a Land Rover and a BMW.

Her definition of being middle-class goes beyond the material possessions.

"In my opinion, being middle class means having quality of life and good taste for beauty and art," she says.

Bei tries to live up to this standard by going to the gym four times a week, collecting art and traveling abroad at least three times a year. Unfortunately, she finds some basic elements of life such as clean air, water and safe food beyond her.

To compensate, she buys organic food, imported milk and bottled water, and has two Swedish-made air purifiers working in her house, and that of her parents.

Bei got divorced two years ago. Being single again at 35 does not bother her, although being misunderstood by her friends does.

"I think I am leading a pretty cool life, but they think I am just putting on a brave face." The issue is finding the right partner.

"Men my age who are equally sound financially tend to choose younger women," she says. "I must say people today are living a more improved life, and they are much more open to life choices than in my parents' era. But, some fundamental changes need time."

She illustrates her point by citing her traveling experiences.

In her three trips abroad every year, she always travels business class, but not all her boyfriends have taken to that very well.

"Oddly enough, I cannot pay for them, because that will bruise their egos even more," she laughs.

Han and his wife and Bei all agree on one thing though, and that is China's middle class needs to be more committed to society and community.

Han uses Weibo to post his opinions on inflation and air pollution, and Bei practices a strict moral bottom line in doing business.

"I will not deceive my clients with lame products, even if some people may be earning more money by doing so," she says.

Professor Zhou of Renmin University expects even more from the Chinese middle class, estimated by the Organization for Economic Cooperation and Development to take up about 40 percent of China's population by 2020.

"The Chinese middle class struggles between tradition and rapid social changes," he says.

"They yearn for a better sense of stability and security when growing their wealth. I believe that with their education and insight they will play a significant role, and their voices on social causes will get louder as they grow more and more numerous."