This southwestern city has dwarfed the country's political and economic centers as the only provincial-level municipality listed among China's happiest 10 cities in 2010 on Sunday night.

Workers from a local community in Yongchuan district, Chongqing municipality, sing revolutionary songs with children left behind by parents working away from home at a local school on May 26. The circulation among the public of revolutionary songs is one of the reasons Chongqing was named one of China's 10 happiest cities this year.

The secret recipe for its residents' happiness, the judges and survey respondents said, is its massive crackdown on organized crime coupled with locals' love of singing revolutionary-era songs.

The annual happiest cities list complied by Xinhua News Agency affiliate Oriental Outlook developed criteria based on people's feeling of happiness rather than economic achievements.

The 12 criteria include interpersonal intimacy, job opportunities, educational quality, security, traffic, medical professionalism, housing prices, natural environments, economic development, culture and entertainment, and civility.

This year's assessment was based on 24,000 valid questionnaires, 1.78 million respondents' replies to newspaper polls and an additional 45 million polled online from September until November, the list's organizing committee said.

Chongqing's war on crime and its love of "red" songs are unique among listed cities.

More than 15,000 students and teachers from local universities "frequently" assembled this year to sing red songs, the official newspaper Chongqing Daily reported.

Most residents say they cannot tell if they are happier than last year, but they have noticed positive changes.

Porter Han Kailiang, 63, said the city is indeed safer.

Two years ago, thugs posing as T-shirt promoters brought Han and several others to a backstreet "warehouse" where they robbed them.

"We can now easily seek help from traffic and patrol police officers stationed anywhere," Han said.

Architect Tang Guangyong said he could "sense the changes and improvements".

Infrastructure development has been particularly fast, the 27-year-old said.

"The city is cleaner, neater and more comfortable. Old people spend their free time playing cards and Chinese chess. That's very nice."

The 10 cities that made the list are Chongqing, Chengdu and Kunming in Southwest China; Hangzhou, Nanjing and Wuxi in East China; Changsha in Central China; Guangzhou in South China; and Changchun and Tonghua in Northeast China.

Chongqing, Wuxi, Guangzhou and Tonghua replaced last year's listings of Ningbo, Xi'an, Yinchuan and Nanchang.

Guangzhou's inclusion stems from its efforts to improve the city's "name card", the organizing committee said, while Tonghua ranked highest in interpersonal intimacy.

Ten counties were also named the happiest out of 60 candidates nationwide.