Shares of Google parent company Alphabet sank on Thursday by as much as 15.8%, putting the company on course for its worst single-day drop in history.

The plunge also instantly wiped out more than $550 billion in market capitalization, also ranking as the company’s worst one day market value loss ever. It also ranks as the second-worst wipeout in market history, only behind Nvidia’s $589 billion drop in 2025.

Google is still America’s fourth largest company by market value, and its shares are worth more than $3.4 trillion, all told.

But the sharp drop in its stock price Thursday was the latest sign of a broader anxiety creeping through Wall Street over how long it will take big artificial intelligence companies to see consistent…