The FTSE 100 index jumped 4.3% to stand above 4, 000 for the first time since February, while Wall Street's Dow Jones industrial average surged above 8, 000, a rise of more than 3%.

Since The Economist costs just $6.99 (a little less than two burgers) on the news-stand, the index provides decent value for money for would-be currency speculators, the authors conclude.

Bingli - who has been studying martial arts for 32 years since the age of just seven - can stand upside down supporting himself on just one index finger.