Assuming two books disagree when they do not

Most operators copy a small number of originating books with a short delay. Two apparently different prices are frequently the same price at two different ages.

Copying is cheaper and safer than pricing independently, so the market has far fewer genuine opinions in it than it has brands. A stale number is usually about to move rather than available to be taken.

Genuine disagreement does exist, particularly on thin markets and in sports the copying books model poorly. That is where line shopping earns most of what it earns.

Here is the catch. The number of available operators suggests far more independent opinion than actually exists, which makes the market look softer than it is.

What to do with it. Learn which books originate prices in your sport, and treat everything else as a delayed copy of them.