A flexible retirement plan, piloted in Shanghai, has proved unattractive to those of pensionable age and employers, according to experts.

Under the plan, launched in October 2010, people in technical and professional positions can decide to push back their retirement, while lower-skilled employees can also apply if they reach an agreement with their company, regardless of ownership or size.

That means men can extend their working life from 60 to 65, while women can continue working until their 60th birthday, instead of calling it quits at 55 for civil servants or 50 for ordinary workers in Shanghai, the "oldest" city in the country.

People over 60 will make up 30 percent of the total population in 2015, according to estimates, when the population of the age group reaches 4.3 million, the Shanghai Civil Affairs Bureau said.

Many countries have pushed back their retirement age to cope with an aging population and a lack of labor.

However, Zhou Haiwang, deputy director of the Shanghai Academy of Social Sciences' Institute of Population and Development, said only a small number have appeared to take up the option to work longer.

"Only about 1,000 retirees applied to keep on working since the implementation of the pilot, very small compared to the more than 1 million retirees every year in the city," according to a Shanghai Business report in July 2012 that cited the Shanghai Human Resources and Social Security Bureau.

The authority declined to provide a more up-to-date figure when contacted by China Daily this week.

However, Zhou said research by his institute had showed the proportion today remains almost the same.

Instead of pushing back retirement, more people opt to retire, he said. "About 20 percent of men retire before 60," he added.

Early retirement is more common in small cities, said Tang Jun, deputy director of the Chinese Academy of Social Sciences' Research Center for Social Policy.

"The average age for retirement nationwide is 53. The intensity and duration of blue-collar work can be tough," he said.

Zhou said that as rehiring someone after retirement seems more beneficial to both the employer and the employee, more opt to do it rather than postpone retirement.

"If someone goes back to work after retirement, he or she can get a pension and a salary for re-employment, which is higher than a pension," he said.

For a business, it is more costly to employ those who push back retirement, Zhou said, as it needs to pay for their social and medical insurance as they keep on working.

"It's also a smarter choice in many cases to re-employ retirees as they're familiar with the work," Zhou said.

He Qingyu, who retired in August, chose to be re-employed at an administrative position at a Shanghai university. He said 80 percent of his peers did likewise, except those who no longer felt physically capable of working.

"People re-employed after retirement mainly work as assistants, so the work is pleasant instead of being oppressive," he said.

Unlike He, 56-year-old Feng Yifang, who retired in October from a banking institution, chose to work for a consultant for a foreign company.

"I can get a salary from my new boss and a pension. Businesses are also keen on hiring us because they aren't required to pay our social insurance," said Feng, who gave herself an English name, Yvonne, to cater to the culture of foreign enterprises, where employees usually call each other by their English names.

However, it is essential for the government to give incentives to retirees to push back retirement as they may serve as a supplement in some areas of employment, such as traditional Chinese medicine and some technology domains, Zhou said.