The Globe and Mail reports in its Wednesday edition that stock markets are thriving again this year, but volatility is growing. The Globe's Tim Kiladze writes that shares of PayPal slumped 11 per cent after it issued subdued earnings expectations. On Tuesday, Shopify dropped 13 per cent on a weaker outlook, despite beating revenue expectations. For weeks, analysts and portfolio managers have predicted that stocks were getting so frothy that there was no room for error, particularly in the technology sector. "Optimistic growth expectations, pricey valuations, and companies failing to deliver can easily create large reversals," analysts at Bank of Nova Scotia warned clients earlier this month. Yet the prevalence of such sharp market swings also suggests something more structural is at play: They can also jump on an earnings report. Meta Platforms, for instance, recently climbed 20 per cent in a single day. Money managers are still trying to figure out the driving forces, but some believe the rise in options trading by retail investors is putting more emphasis on individual events. The managers also think the growing number of quantitative funds that use trading algorithms can exacerbate market moves in either direction.