Japan's Tokyo - last year's winner - and the British capital London took second and third places in the Innovation Cities Index, with the U.S. cities of Los Angeles, Chicago and Boston also making the top 10.

"What really surprised us this year was a United States bounce-back at the top of the league," said Christopher Hire, director of commercial data provider 2thinknow, which publishes the annual ranking of 500 cities.

Chicago entered the top five for the first time since the poll began in 2007, due to a burgeoning number of start-ups and top-ranked universities, the index found.

One of the big losers was the San Francisco Bay - home of the Silicon Valley headquarters of tech giants like Apple, Facebook and Google - which fell six places to ninth spot due to "tech controversies, homelessness and privacy issues", it said.

All three firms have pledged billions to ease California's housing crisis, as fast-growing tech companies have drawn protests from Northern California residents who blame them for rising housing costs.

In the run-up to the 2020 U.S. presidential election, Big Tech companies are being challenged across the political spectrum, from privacy concerns to their policies on political ads and ensuring election security.

The index looked at more than 100 indicators including transport, infrastructure, citizen privacy, green architecture, property prices, start-up office spaces and internet users.

Several Chinese cities made gains, including Beijing and Shanghai, in a sign of rising global power, 2thinknow said.

"Our Index is designed to measure innovation conditions, and often predicts rising cities before other rankings," said Hire.

"It is up to the city whether they can keep on top of the latest trends, and exploit their innovation potential."

China is preparing to become the first country in the world to roll out a digitized domestic currency - powered partially by blockchain technology and dispersed through digital wallets - in a move closely watched by financial services.

London, Paris and Berlin were the only three European cities to make the top 20, fewer than in previous years, while African cities fared worst, languishing at the bottom of the index.

REUTERS