In January, Valve released a major update for the team-based shooter Deadlock with a new mode and characters. As it turns out, the release date could be predicted using the "pizza index."
Streamer VegasDeadlock noticed an anomalous surge in orders at pizzerias located around the Valve office.
VegasDeadlock linked this to Valve preparing to release the Deadlock update — shortly after his publication, the update actually came out.
It seems that now, thanks to the streamer's discovery, fans of other Valve games have found a new parameter for tracking potential announcements or updates.