In a sparkling white cap and oversized sunglasses, 55-year-old retiree Zhang Yongli and dozens of neighbours liven up a Shanghai park by doing the jitterbug, part of a public dance craze that has become China’s national pastime.Every day, an estimated more than 100 million people -- dubbed “dancing aunties” as they are primarily older women -- take over squares and parks to tango, waltz, and grind out everything from flamenco to Chinese traditional dance.Complaints over speakers blaring late at night have ensued, and even physical brawls pitting aunties against others vying for park turf. But toes are tapping to an ever-quickening beat as “square dancing” -- as it is known in China -- booms.Teams are competing in dance-offs featuring thousands of contestants, while a thriving market of dance-related paraphernalia and mobile apps catches the attention of the business world. Even the government has jumped on the bandwagon to extol the health benefits.AFPA square dancer practising back stage at the final round of a city-wide square dance competition at a local theatre in Shanghai.“Square dancing happens wherever there is a square,” said Wang Guangcheng, a fitness instructor and choreographer who helps the government devise dance routines and is widely known as China’s “Square Dance Prince”. “It has become a venue for the masses to exercise.”- Shaping up -More than 240 million Chinese are 60 or older, a number expected to double by 2050. By then, the government estimates China will be spending more than one-quarter of GDP on elderly care and medical services, compared to around seven percent in 2015, placing increasing importance on healthy, active lifestyles.Zhang “was sitting at home, doing nothing” after retiring five years ago from her travel-agency job, undergoing treatment for diabetes, high blood pressure and cholesterol. “Since I started dancing, my (health) indicators are now normal. I no longer need medication,” she said as her neighbourhood dance group’s red skirts twirled in Shanghai’s Zhongshan Park.“I also look younger,” said Zhang, who has jitterbugged away 11 kilograms (24 pounds) of bodyweight. A 2016 national fitness plan stresses “square dancing” as a team sport to be “vigorously developed” and last year it became an official event at China’s National Games along with old reliables like athletics and swimming.Local contests are proliferating. Shanghai retiree Li Zhenhua’s team worked with a professional instructor for weeks, enduring the winter chill and the summer heat of their local square to train for a months-long citywide contest that culminated in August.The team, drawn mostly from China’s ethnic Korean minority, took the title with their traditional Korean dances, beating out 750 other troupes. “I was happy to find a Korean ethnic dance team in Shanghai, not only to exercise and dance but also to pass along our ethnic culture,” Li said.AFPA woman from a square dancing team striking a pose for a photograph in a public park in Shanghai.- ‘Silver’ economy -Mass public dancing took root after the 1949 Communist takeover as the government organised communal activities to foster unity and loyalty to the party. But it has really taken off lately as an increasingly prosperous China finds more leisure time, and nearly every neighbourhood park or square today is enlivened by dancers availing themselves of the free exercise.Taobao, the leading Chinese e-commerce site owned by Alibaba, and other businesses are expressly targeting the new market to sell clothing, speakers, and gadgets for watching and learning new dances, and market studies say the industry is booming.Han Xiaoyuan, 28, founded a mobile platform for organising competitions and purchasing gear. User numbers quintupled over the past two years to more than 500,000. It is also one of many business initiatives seeking to tap into the wider “silver economy” represented by dancers, by selling travel packages, financial services and other products geared towards retirees.Han said the elderly “have time (and) money.... They are our best business target group”. Square dancing is even changing age-old gender dynamics, as grandmothers are often away training for long stretches. “Several of our team members’ husbands have learned to change diapers and taken over feeding the grandchildren as a way of supporting us,” said 65-year-old Hong Aizhen, a competitor in the Shanghai-wide contest.But many men are showing off their dance moves as well. Late one recent weekend, hundreds of people filled a tree-lined park in central Shanghai amid a cacophony of musical styles as men and women waltzed or formed conga lines, and children did the cha-cha.Often, they dance to old Chinese revolutionary standards or other patriotic tunes. “We are not only delivering a fitness culture, but also the concept of a prosperous country,” said choreographer Wang. “Many songs we choose express our national characteristics and values.”But dance enthusiast Zhang prefers the zesty jitterbug. “It’s quick and rhythmic. I forget all my worries when I dance, sometimes even my age,” she said.