Line setting

Makers and copiers

There are two kinds of book. The first kind makes its own line: an oddsmaker rates every team, turns the difference between two ratings into a point spread, adjusts for where the game is played, injuries and rest, and puts the number up before anyone else has one. That is the opener.

The second kind waits. It watches what the first kind posts, lets sharp players bet into it, and copies the number once it has settled. Most books are the second kind, and so is nearly every local bookie. An agent using a per-head office doesn't make a line at all; the office sends it to his players, and the office is following the market too.

I have nothing against copying. It is cheaper and safer than having an opinion. It does mean that the same number at ten books is one opinion, not ten.

How an opener becomes a line

An opening number goes up with low limits on purpose, because the book is paying for information, and the first people to bet it are the ones who do this for a living. Where they bet tells the book where its number is wrong. The book moves, the sharps bet again or stop, and after a few rounds the line holds still. Then the limits go up. By game day the book will take many times what it took on the opener, because it now trusts the price.

That is why I wouldn't bet an opener unless I knew something. The number is at its weakest then, and so are you, against the people who bet it for a living.

It is also why the closing line is the best estimate of a game there is. It has been bet into by everybody with an opinion and money. See closing line value for how to use that.

The right number, shaded

You will read that the line is set to get equal money on each side. It isn't, quite.

A good bookmaker tries to put up the right number, the one where he would be happy to take either side, and if the number is right he doesn't need the money to be even, because the vig works for him over time whichever way the bets fall. What he does do is shade. He knows the public likes favorites, popular teams and overs, so the popular team that should be -7 goes up at -7.5. The public bets it anyway. The half point costs them, and anyone who wants the other side gets a slightly better number than the game deserves.

Shading is small (a book that shades by much gets picked off by sharps taking the other side), but it is real. If you like the unpopular side, you are usually getting a little extra, and I'd always rather be the man collecting that half point than the one paying it.

Key numbers

Not every half point is worth the same. In the NFL, games end with a margin of exactly 3 more often than any other number, and 7 is next. A spread of -3 and a spread of -3.5 are much further apart than -4.5 and -5.

A bookmaker treats those numbers with care. Rather than move off 3, he moves the price first:

• -3 at -110, the standard.
• -3 at -120. You now risk $120 to win $100, and need 54.55 percent winners in place of 52.38.
• Only when that isn't enough, -3.5.

So in football, read the price as well as the spread. Two books can both show -3 and be offering different bets. I'd pay for the 3 and the 7 and not worry much about the other half points.

One opinion, three prices

The oddsmaker's ratings produce a predicted margin and a predicted score. The margin becomes the point spread, the combined score becomes the total, and the spread is converted into a moneyline from a chart of how often a favorite of that size wins the game outright.

That is why the three move together. If the spread goes from -3 to -4 and the moneyline hasn't changed yet, one of them is stale.

Compare the number across books as well. How a book's line differs from the market tells you where it has taken a position; more on that under odds movement.

The line is the bookmaker's best guess with the vig added, and it is hard to beat. Let that set the size of your bets: small against your bankroll, with a loss limit you decided on beforehand. A lot of smart money went into that number before you arrived.