Data Done Wrong

 | Oct 10, 2017 09:07AM ET

A quarter of a century ago, when I ran Prophet’s first advertisements, I used the deadline “Data Done Right” to stress the importance of cleanness in our data. I must say, however, there’s something in the financial information industry which has had all those decades to get right but still hasn’t, and it’s these “after hours” pages big financial sites run.

Ostensibly, these are places where big after-hours moves, both up and down, are highlighted. They could be driven by earnings, corporate news, or anything else, and if the data was accurate, they would be awfully interesting both after the market closed as well as in the morning before the open. The problem, though, is this: