Facebook owner Meta scored its biggest ever one-day loss in market value on February 2 this year, shedding a fifth of its worth after a disappointing earnings announcement. Two days later, Amazon recorded the biggest one-day gain—a 13% rise—after a positive announcement.

Such moves are the stuff of nightmares for options traders, who must hedge against the price moves such surprises can cause.

Quants at Citi have built a model that can help.

“It gives us a better idea of how our book is going