Reading the order book shows you who is willing to buy and sell a prediction market share, and at what prices, before you place a trade.
Bids and Asks
Bids are offers to buy; asks are offers to sell. The highest bid and lowest ask form the top of the book, and the price you see is usually close to them.
Depth
Depth is how many shares sit at each price level. A thin book means a larger order may move through several levels and fill at worse prices.
Reading Changes
Watching how orders appear and disappear can hint at interest, but large orders can also be cancelled. Treat the book as a snapshot, not a promise.
Worked Example
The best bid for YES is 47¢ for 300 shares and the best ask is 50¢ for 100 shares, then 52¢ for 200. Buying 250 shares at market would fill 100 at 50¢ and 150 at 52¢, an average of about 51.2¢.
Key Takeaways
- Bids are buyers, asks are sellers.
- Depth decides how far a large order moves the price.
- Calculate your average fill before trading.
- The book can change in seconds.