$GameStop(GME)$Participation by retail traders swelled to 24 per cent of all US stock market action during the first quarter. Stocks the group favoured soared, including a 1,600 per cent rally in January by GameStop. But those bets turned sour in the second quarter, with some of the Reddit targets falling more than 50 per cent.

At the same time, demand for cryptocurrencies surged, sending some alternatives to bitcoin into eye-popping rallies reminiscent of the meme-stock frenzy. That buying has started to show signs of cooling, with Tesla's Elon Musk denting the price of bitcoin with back-and-forth utterances on the electric-car maker's plans for the token.