To add to that last sentence by Redietz, many whales now have the ability to wager huge amounts directly into the pools in milliseconds directly from their computer. Because of the amount that they bet, they go directly into the pool, not through a wagering site like the rest of us. So they have a computer analyzing all of the pools for overlays and then when an overlay is found it triggers the bet. No actual handicapping by the player. It is these huge amounts that cause the huge drop in odds right after the race goes.

It is not past-posting as many suggest. it is just computer generated wagers.

We used to past post at Maywood (RIP) but that is another story