How Often Do Underdogs Win Outright?

Naturally there are different levels of underdogs and if you know me by now, you know that I will head to my computer and get all the details. There has been a lot of college football played since 1997, 17 years worth of it. If you count each FBS team playing a game (so 2 teams each game) in that span there were 24,214 different games of data for me to analyze.

Let’s look at the biggest favorites and you will see that Las Vegas does its job well picking out big favorites. Since 1997 there have been 756 teams that have been favored by OVER 31.5 points in a game. Of those 756 only SEVEN have lost the game straight up. The biggest upset ever was when Stanford (+41) upset USC in 2007 and showing what a weird year that was, the 2nd biggest upset ever was also in 2007 when Syracuse (+37) beat Louisville. The other 4 huge upsets since 1997 were: Texas St (+36.5) over Houston in 2012, Temple (+35.5) over Virginia Tech in 1998, Central Michigan (+35.5) over Western Michigan in 2000, James Madison (+35) over Virginia Tech in 2010 and North Texas (+32) over Texas Tech in 1997. Basically if your team is installed as an underdog of 31.5 points or more in a game, they have a 0.9% chance of winning.

Now let’s look at the chances of your favorite team winning if they are installed as an underdog of 24.5 to 31 points. Since 1997 there have been 902 teams that have been favored by 24.5 to 31 points in a game. You would expect the underdogs would have a better chance of winning outright than the above teams and naturally they do. In that span 36 teams that have been favored by that margin have lost straight up in a game with four such upsets last year. Nicholls St was +28.5 when they upset Western Michigan, Georgia Southern was +28 when they upset Florida, Eastern Washington was +27 when they upset Oregon St and Penn St was +24.5 when they upset Wisconsin. The amount of upsets did not go up as much as I thought they would as upsets occurred only 4.0% of the time or 1 out of every 25 games.

You would figure that the percentage of upsets in the 17.5 to 24 point favorites level would go up drastically from that 4.0% in the previous category. Since 1997 there have been 1,522 teams that have been favored by 17.5 to 24 points. I am still a little surprised that there were only 97 upsets in this level of favorites over the 17-year span. That is just 6.4% upsets, which comes out to 1 upset loss for every 15.6 teams that are favored by 17.5 to 24 points. Last year there were three such upsets which included McNeese St over USF, West Virginia over Oklahoma St and Central Michigan over Ohio.

I will start breaking it down into smaller categories as we continue to go down in level of favoritism. The next category to look at are teams that are favored by 14.5 (more than 2 TD’s) to 17 points. Since 1997 there have been 984 teams that have been favored by 14.5 to 17 points in a game. Of the 984 teams favored by this amount 127 have lost the game outright. That is double the odds as the category above as 12.9% of the teams favored by 14.5 to 17 points lose outright and an upset occurs 1 time for every 7.7 games played in that level. There were only 8 such upsets last year including UCF over Louisville.

The next level down that I will look at is the 10.5 to 14 point category. From 1997 – 2013 there were 1,656 teams that were favored by this level. Of those 1,656 games there were 346 upsets, which was 20.9% of the time. That still means that roughly 4 out of every 5 teams favored by 10.5-14 points wins the game with an upset occurring once every 4.8 times.

From 1997-2013 there were 1,543 teams that were favored by 7.5 to 10 points and of those 1,543 teams there were 399 upsets, which was almost the same results as the favorites from 10.5 to 14. That means that 25.9% of the time a team was favored by 7.5 to 10 points they lost outright and that translates into 1 upset every 3.9 games.

Since 1997 there have been 2,854 teams that have been favored from 3.5 to 7 points. These are teams that are expected to win the game but the game should be close. The last time we tightened up the category the upsets went from every 4.8 games to every 3.9 games. Should we expect 1 in every 3 games here? Since 1997, 997 of the 2,854 teams that were underdogs of 3.5 to 7 points have pulled outright upsets and that translates into 1 every 2.8 games or 34.9% of the time.

Now we get to the category that will tell us if Las Vegas knows what they are doing. Games where a team is favored by 3 points or less. These games are basically toss-ups but Vegas favors one team and makes them the favorite. What percentage of teams pull minor upsets as underdogs of 3 points or less? As I type this I do not know the answer, but I will guess 45% of them. Now let’s go to the computer. Since 1997 there have been 1,890 favorites of 3 points or less. My 45% guess would have 851 minor “upsets”. The actual answer is 892 “upsets” by teams that are underdogs of 3 points or less which comes out to be 47.2% and that shows these games are definitely toss-ups! 

Here is a quick chart showing the chances of a team winning outright depending on where Las Vegas sets the line.

Now instead of looking at 17 years of data, let’s just look at the last 5 years. You would think that with the parity in college football that these % of upsets would be higher but overall that was not the case. In fact, 6 of the 8 categories actually saw a decrease in the chances of pulling an upset highlighted by underdogs of 3 or less only winning outright 43.41% of the time, a 3.78% decrease from the last 17-year data.

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