How Sports Books Create Betting Odds

When it comes to sports betting odds, there are two terms you will frequently hear, “opening lines” and “closing lines.”

Opening lines in sports betting refer to the first set of odds released by the sportsbooks for a particular event. Depending on the event and type of bet, opening lines may be available hours before the start time or months or weeks before.

Keep in mind that the opening line is only a starting point. It is a beginning place for skilled bettors to enter the market and attack the line as they see fit.

In contrast to the opening lines, there are also closing lines.

Closing lines in sports better refer to the last betting odds available before the event starts. 

Typically the closing line is considered the sharpest line available and represents the actual probability outcome of the event. Since the most information is available at the start time, sports books can make the odds the most accurate on the closing line.

Many sports bettors use the closing line to compare the odds they received on their bet against the final odds available. This is known as the closing line value.

Sports books can take a few different approaches to set their opening odds as well as how they move the odds up until the closing line.

Is there one sportsbook in Las Vegas setting all the lines?

No, there are many sportsbooks in Las Vegas and worldwide, and they all set their lines. There is no single sportsbook that sets the lines for everyone. However, many sports books will follow the lead of other sports books. 

There was a time when most betting lines did originate in Las Vegas. The line was gradually shared all over the country and globally and, more often than not, tweaked along the way.

When people talk about “Vegas” and what the line is, they usually talk about a line agreed upon by whatever they believe to be the most reputable bookmakers.

How are betting odds set?

Betting odds are set using many factors available about the event. Many sportsbooks use statistical models to create betting lines, factoring in known and unknown data probabilities. Some sportsbooks pride themselves on always opening the first line.

Sportsbooks usually use limits to manage risk to various outcomes when setting opening lines. Professional bettors will typically wager aggressively with opening lines depending on whether or not they see a profitable opportunity.

Sportsbooks may adjust their lines to reflect their bets depending on which side the sharpest bettors place their bets on.

Many sportsbooks simply follow the opening lines of other books. As time passes and errors are corrected, more bookmakers worldwide become more comfortable following the opener sportsbook consensus line as their own.

Why do odds change in sports betting?

The odds and betting lines in sports betting can change for various reasons, including sharp betters indicating what they believe is the likely outcome, lineup changes, or late news such as weather or player injuries.

An example of late news that can affect betting odds is the weather forecast in baseball.

As time goes on after posting the opening line, sports books will closely monitor how much liability they have on one outcome and their calculated probability of that outcome happening. Liability for sportsbooks simply means how much they stand to lose.

Some sportsbooks use public betting to move odds in one way or another in order. This is an example using wisdom of the crowd in sports betting. This theory assumes the consensus of a large collection of people is more intelligent than individual experts.

Line Shading in Sports Betting

Line shading is a practice used by sportsbooks to protect themselves from sharp bettors.

For example, let’s say the Philadelphia Eagles are playing the New York Giants, and the Eagles are favorites. The opening line is set at Philadelphia -8.5. This means the Eagles must win by 9 or more points for their bettors to win their wager.

The oddsmakers set this line in anticipation that the public will primarily bet on the Eagles. However, they want to shade the line towards the Giants to draw in more money on that side.

They know that once they move the line closer to the proper line of Philadelphia -6.5, they will already have offsetting money on the other side.

Wrapping Up

Oddsmakers use a wide variety of techniques to create their betting odds. Some will use complex models, while others simply follow the wisdom of the crowd (of other sportsbooks) to set their lines.

Many factors can influence how these lines are set, and they are constantly changing as more information about the event becomes available.