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Checkdowns: How likely to be a close game?

Posted by Chase Stuart on February 6, 2011

Good post by Nate Silver over at the NYT Fifth Down Blog. I thought I'd build on some of Nate's work.

As of game day, the Packers are 3-point favorites over the Steelers and the game has an over/under of 44.5 points. Over the 20-year period from '88 to '07 (we're a little behind at entering point spread data into our database), there were 425 games that featured a point spread of between 2 and 4 points with an over/under ranging from 42.5 to 46.5. Some notes on those games:

  • Based on the above numbers, the favorite has won 63.5% of the games, with an average margin of victory of 11.4 points.
  • The biggest blowout came against the Steelers in a season opening game against the Browns. Cleveland opened the 1989 season as 2-point road favorites: they covered the spread with ease, winning 51-0.
  • On average, when the underdog wins, they win by 8.7 points. Atlanta started the 1996 season 0-8, but after squeaking past Carolina 20-17, they were 2 point favorites in St. Louis, who had just lost 42-6 in Pittsburgh. The 2-7 Rams pulled the upset, winning 59-16.
  • On average, the favorite has scored 24.3 points while the underdog has scored 20.2 points. Favorites, against the spread, have a 209-197-19 record. The "over" was hit less frequently, with 195 games going over, 11 games "pushing" and 219 games finishing "under" the line.
  • 121 of the games, 28.5% of the data-set, had final margins of victory of within three points. If you're hoping for a close game, there's a better than even chance you'll get one: 53% of the games were decided by one touchdown or less. Only 16 games had final margins of 30 points or greater, but just over one in every four games were decided by at least 15 points.
  • Hoping for the first Super Bowl to go to overtime and the first playoff game to feature the new overtime rules? 5.8% of the games in this data set went into a fifth quarter.