Median odds, top, bottom and spread — the OddsHistory summary columns

On every comparison view in OddsHistory you'll see four summary columns next to the per-bookmaker prices:

• Top — the best (highest) decimal price published across the operators covered. This is the price you would actually take if you walked through every site one by one.
• Bottom — the worst (lowest) decimal price. Useful for spotting operators that are reliably tight on a market.
• Median — the middle price. With ten bookmakers covered, this is the average of the 5th and 6th prices when sorted. We use median rather than mean because it isn't dragged by a single stale price or an outlier promo.
• Spread — top minus bottom, in points. A three-point spread on a $5.00 runner means a noticeable disagreement; a five-cent spread means the market is tight.

Median is the right anchor for "what is the market saying right now". The overround we quote on every market uses median prices for this reason. And spread is the simplest way to see when there is room to look for price movement ahead of the rest of the market.