今天的经济学家杂志说，中国人教了美国人两个东西：炒破产股、频繁炒波段。

To understand the new wave of small investors, look to China

Speculation is as old as the hills, but you can count on some variations.

There is nothing new on Wall Street. Speculation is as old as the hills. So says the protagonist of “Reminiscences of a Stock Operator”, published in 1923. Quite so—but you can count on some new variations. Take the case of Nikola Corporation, which makes trucks powered by green energy. On June 8th its stock price doubled. It was then worth more than Ford. Yet it has sold no vehicles. “Sympathetic magic”, explains a seasoned investor. Nikola is named after Nikola Tesla; as is Tesla, the leading electric-vehicles firm. That is enough of a buy signal.

Enough, that is, for a new army of retail speculators, which is blamed for a lot of strange moves in stock prices. Since March, no-cost brokerages that cater to small investors report a dramatic surge in new accounts and trading volumes. A noisy gaggle of social-media and chat-room pundits has emerged. David Portnoy, a sports-betting media-mogul reinvented as “Davey Day Trader” is perhaps the most prominent. The retail army has marched into America’s evergreen tech stocks. Less predictably they are also keen buyers of grounded airlines, of beached cruise liners and, strangest of all, of Hertz, a car-rental firm that has filed for bankruptcy.

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