Gambling is illegal in China. Playing the stock market is not. And so in the past few weeks, markets have sizzled as retail investors “stir-fry” stocks (the local jargon for speculation). Yesterday saw the first severe day of profit-taking since the rally began — Shanghai shares fell 5 per cent — but volumes continued to rise. The day’s turnover reached $128bn.

China’s securities firms will enjoy the heat. Average daily trading volumes in Shanghai and Shenzhen in December have been about $110bn, compared with a daily average in the first half of $17bn, according to Bloomberg. Investors have connected the dots. Bloomberg’s index of Chinese brokers has nearly doubled since late October.

So, the index is no longer cheap. It trades on 38 times earnings estimates for 2015. Those forecasts look conservative, but how conservative is hard to say. Citi Research suggests that earnings at China’s top two listed brokers, Citic Securities and Haitong Securities, could increase as much as 130 per cent if next year’s turnover averages $90bn a day, or nearly twice that of 2014.