Football and basketball totals are made in the same manner as point spreads, as they’re designed to attract equal amounts of money coming in on both the over and under. Once again, for the sportsbooks, a balanced ledger that makes a profit regardless of the final score is the ideal situation.
Baseball and hockey totals more closely resemble money-line odds. The books often know they’ll receive more money on the under or over on a particular game, but are hoping to attract enough bets on the opposite to balance their books. When a sportsbook releases a total on an NHL game of 5-over (-140), meaning you must risk $140 to win $100 if you bet the over, it has a good idea there will be more over than under bets, but is hoping to attract enough under bets to cover their losses should the game land over the total.
The sportsbooks also know that they’re likely to receive more over bets on a game than they are under bets. The betting public likes to bet overs, as it’s more fun to root for scoring than it is for defense. As a result, totals are often slanted a bit towards the over, especially in football, which is the most popular betting sport, and that’s the reason most smart bettors will wager on more unders than overs. In the 2017 NFL season, overs were 111-132-8 (45.7%). In college football, overs were 364-428-21 (46%). Those percentages are a bit lower than they have been long-term, but both the NFL and college football are also under 50% overs since the start of the 2000 season.
Just like point spreads and money lines, totals move due to money wagered. If more money is being bet on the over, the books are likely to raise the number to try and attract bets on the under and discourage bets on the over and vice versa. As you saw earlier, the number raised in football or basketball is the total—from 43 to 43.5 in football, for example; in baseball or hockey, the odds go up, from 8-over (-115) to 8-over (-120), for example. Again, injuries, suspensions, and the weather can cause totals to move.
Unless it’s an injury to a star quarterback, such as Tom Brady or a Baker Mayfield in college football, injuries or suspensions don’t have a big impact on totals and weather is the the biggest influence on totals. Football games played in freezing weather will see the total drop, while in baseball the Chicago Cubs are the best example, as their totals can be 11 or 12 if the wind is blowing out and 8 or 9 with the same two pitchers if the wind is blowing in.