The Truth Behind the 12-5 Upset

Everyone knows that you can’t fill out a bracket without picking at least one 12 seed to upset a 5 in the first round. While this well-known phenomenon has been backed up with data showing that it truly does happen more than you would expect, there has been almost no study into why exactly it happens. That is, until now.

The truth of the matter is the 12-5 upset isn’t a thing. Well, it is, but it only really applies to certain teams. Looking back over many years of NCAA tournament history, when you separate out power conference and small conference teams, it is only the 12 seeds from the big conferences that outperform what you’d expect from a 12 seed, while the small schools perform at a rate almost that is, well, exactly what’d you expect.

Looking all the way back to 1985, when the field expanded to the 64-team format (play-in games are not included in this analysis), power conference (ACC, Big 10, Big 12, Big East, SEC, Pac 12) 12 seeds have taken down the 5 seed 55% of the time, compared to only 32% for small conference (all other than the 6 conferences mentioned above) schools. This is not just an old phenomenon either, in fact quite the opposite, as the big schools have won 77% of the time over the past 20 years compared to 33% for the small schools. When looking at the past 10 years, it climbs even higher to 88% compared to 34%, and over the past 5 years all 5 power conference schools to be a 12 seed have won, while just 35% of the small conference schools have. Considering 11 seeds win at a 36% clip historically, it is clear the small schools are performing about how you’d expect from a 12 seed, while the big schools are the ones creating the mirage of all 12 seeds over performing.

Now, the natural reaction to this information is that power conference teams are always going to outperform the small schools, and it is not just the 12 seeds. In reality, however, that is not the case. Over the past 10 years, 11 seeds from the small conferences have a better first round winning percentage than their power conference counterparts. Same with 10 seeds, and 9 seeds, and 8 seeds. While there is nowhere near as big of a separation as there is with the 12 seeds, it shows that it is not just a case where big schools outperform their seeds. In fact, comparing performance across seeds 1 to 11 over any recent timespan, there is no notable difference in performance in the tournament between the big and small schools. While it is certainly clear that big schools overall have more success, they also tend to be seeded higher, and once you hold seed constant, the performance is pretty consistent across both groups, suggesting the selection committee has overall fairly seeded both big and small schools.

Also, it is worth wondering whether this is just a product of chance, given the fact that there haven’t been that many 12 seeds from the big schools. However, assuming 12 seeds truly have a 32% chance of winning, the odds that the 55% figure would occur is just 2% when factoring the number of games played. And if you’re more inclined to look at just the past 5 years rather than the full 33-year history, the odds we’d get these results from pure chance are less than half a percent.

Considering this information, it begs the question, what about these teams make them so likely to provide these upsets? It is a bit hard to say, but looking at the teams from recent history provides a bit of a glimpse. The general theme is these teams fall into one of two buckets: teams that got hot in the conference tournament and pulled out an automatic bid to get into the field when they otherwise would have been on the outside looking in, and rode that momentum into the tournament, while the other group is teams that crashed out early in their conference tournament, likely causing them to be under-seeded from one bad performance when their resume from the whole season merited a higher seeding. There was not a single power conference 12 seed to pull an upset who went out in either the semis or championship of their conference tournament in the past 10 years – every single one of them either went out before that point or won it all.

Looking at this year’s bracket, there is not a single 12 seed from the power conferences, but this does not necessarily spell doom for Davidson and their fellow 12 seeds. As mentioned above, small conference 12 seeds have still taken about one third of their matchups, so look for 1 or 2 of them to pull off the upset. After all, anything can happen in March.


The data for this article was supplied by The Washington Post at: http://apps.washingtonpost.com/sports/apps/live-updating-mens-ncaa-basketball-bracket/search/

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