There are a number of people who will know the data and a number of ways of secreting that data out, even if it is just a thumbs up or thumbs down.

True. But then it would be pretty easy to catch who is doing it: just follow the money. See who was selling all those contracts four minutes before release, and find out who their friends inside the organization are.

The fact that it was only four minutes before actually suggest to me that someone has figured out some technical glitch. Say the PDF is put on the server first, then it is linked to from the main page. While most people is waiting for the link, someone might be able to guess the URL and get directly to the report a fraction of time before everyone else.

Another possibility would be itchy fingers: traders not bothering to read the report but looking at the price to react quickly to the reaction. A small drop down and the trader sells, causing more drop and more twitchy traders selling and a small avalanche. 50% chance of being right...