The murmurs began last week, before the Broncos put up 51 points against the Cowboys and the Jaguars lost second-overall pick Luke Joeckel to injury. And when the dust of Week 5 had settled, sure enough, the betting line for Jaguars at Broncos was set at 28 points, which is a lot.
Twenty-eight points is the largest spread of all time, but that doesn't tell the whole story of how statistically improbable this is. According to to "The Handbook of Sports and Lottery Markets," from 1993 to 2000 the average NFL point spread was 5.64 points, and the standard deviation was 3.58 points. This puts a 28-point spread at 6.2 standard deviations from the mean. To compare, that same source puts the point spread of an average NBA game (from 1994 to 2002) at 6.37, with a standard deviation of 3.72. This NFL line is equivalent to an NBA team being favored by 30 points.
Here are some other things that are 6.2 standard deviations from the mean*:
- An NBA player putting up 44.4 points per game (2013 data, scoring title qualifiers only).
- An NFL player rushing for 207.0 yards per game (2012-2013 data, min. 100 rushes).
- A baseball player hitting 73 home runs in a season (2013 data, qualified batters).
- An 18- to 65-year-old American male who weighs 450 pounds (EPA NHANES IV data).
- An 11-inch penis (LifeStyles condom data).
*Point-spread distributions are positively skewed, so take these comparisons with a grain of salt.
Below is a histogram showing the frequency of NFL betting lines from 1994-2012, based on data from Wizard of Odds. The five games that posted at 20 points or higher, and the upcoming Jaguars-Broncos game, are marked with crosses. Not only is this matchup the highest spread in the dataset, it's not even close:
Smart bettors, take note: Of the eight games with largest all-time spreads, the heavy favorite has covered only once. On the other hand, the Broncos and Jaguars are both performing at historical levels, pushing the limits of what it's possible for an NFL offense to do or not do. What we have here is a perfect storm.