CNBC's Carl Quintanilla passes along a Morgan Stanley report that has quantified the amount that stocks fall after a data breach is made public.
Driving the news: Marriott was above average. It fell 5.6% on Friday, after a data breach that could have affected as many as 500 million customers. That's more than the 4% one-day decline Morgan Stanley has calculated after looking at Target, Home Depot, Yahoo, Heartland Payment and Anthem.
- Expect Marriott to pay a hefty fine under Europe's GDPR rules.
- Don't expect a bounce on Monday. After a week, those companies were down even further: 6%, on average, from their pre-disclosure level.
One company that saw no decline in its share price this week: The U.S. Postal Service, which exposed the data of 60 million customers. That's one advantage of being state-owned, I guess.
Go deeper: Behind the Marriott breach's "500 million affected" tally
