The market moved first
For every story we know when the first article appeared and what its market did around that moment. These are the stories where the odds had already moved in the 24 hours before anyone reported it, and moved more then than in the 24 hours after. Traders were pricing something coverage had not caught up with.
Nothing right now. 25 live stories have prices tracked a full 24 hours either side of their first article, and in none of them did the odds move at least 5 points before coverage. Markets are now recorded before a story links them, so this fills in over time.
How this is counted
A story's first article is the earliest publish time among its sources, as stamped by the publisher's own feed. Its market is the best-matched one. We take the market's price 24 hours before that moment, at it, and 24 hours after, from the price changes we record every few minutes. A story is listed when the move before is at least 5 points and larger than the move after. Stories with prices tracked for less than a full window either side are not measured at all, rather than measured badly.
This describes when the odds moved, not why. Feed timestamps can lag a newsroom by minutes or hours, and a market can move on the same event a story reports before the story is published. Nothing here says anyone knew anything.