https://phys.org/news/2018-07-facebook-reality-stock-reeling.html

Shares in Facebook plummeted 19 percent to $175.30 in early trade Thursday, wiping out some $100 billion—believed to be the worst single-day evaporation of market value for any company.

The plunge came one day after the company missed revenue forecasts for the second quarter and warned that growth would be far weaker than previously estimated.