August 26, 2026: Yes, Stocks ARE Having Larger Return Swings

You are not imagining this. Individual stocks are currently experiencing a wider dispersion in daily returns, both up and down, than investors are used to seeing.

On the upside, the moves have been extraordinary. On August 19, Moderna (MRNA) surged 177% after the company and Merck reported positive Phase 3 data for a personalized cancer vaccine. Palantir (PLTR) climbed 29% on August 4, riding enthusiasm around its earnings and AI-driven growth story.

The downside has been just as dramatic. IBM fell nearly 25% on July 14, a stunning drop for a company long viewed as a slow-moving blue chip. Even Walmart (WMT), a stock famous for its stability and resistance to big drawdowns, returned close to -10% on August 20.

What’s driving this? A mix of concentrated index positioning, thinner liquidity around earnings and news events, faster information flow, investor overreaction, and heavier use of options that can amplify price swings. Whatever the cause, the pattern is clear: single-day moves are increasing and, since 2003, have only been higher during the Great Financial Crisis and COVID.

For investors, the takeaway is simple — position sizing and diversification matter more than ever when any one name can swing double digits overnight.

Weekly Market Update: August 26, 2026