The stock price of Zoom Video Communications Inc (stock ticker ZM) spiked significantly, as you would expect given the Zoom hype due to the pandemic.
However, the stock price of Zoom Technologies Inc (stock ticker ZTNO, but at the time ZOOM), a completely unrelated company based in China, went up by something like 1000%, due to what is generally believed to be uninformed day traders who saw "Zoom Technologies" and assumed it was the videoconferencing company.
According to Yahoo Finance, ZTNO has an average daily volume of about 10k shares ($2.5k) so it would be pretty easy to pump the price up. I could probably singlehandedly double the price if I wanted to. It's possible that the 1000% price increase was caused by only a handful (or even just one) trader(s).
This is most of it. EMH can't apply to low float stocks because the ability to borrow is scarce and so the market can't easily correct the price without the supply side taking on enormous asymmetric risk. All it takes is a few million dollars in buying power to keep a small stock up 100 percent and not even the biggest hedgefund can correct the inefficiency.
