The myth of the perfectly balanced book

Balancing every market would remove almost all risk and most of the profit. Books deliberately take positions on games they believe they have priced correctly.

If a book only ever collected the margin on balanced action, it would be a commission business. Taking a side on a well-priced market is where the additional return comes from, and they price well.

Balancing does still happen, particularly on very large exposures and on markets the book prices less confidently.

And that is the trap. 'They just want equal money' is folklore from an era of telephone betting, and it leads readers to conclusions about line movement that are mostly wrong.

What to do with it. Stop reading a still line as inattention. It is usually the book declining to move rather than failing to notice.