Using the The Sosna Upset-Biased NCAA Bracket Pointing System (© 2024, Scott C Sosna, all rights reserved) in your friendly tournament wagering is only meaningful if, in fact, a decent number of upsets occur. The follow-up question therefore must be How prevalent are upsets during a typical NCAA Men’s Basketball tournament? Very prevalent: since 1985, 28.59% of regional games are considered upsets when simply comparing seeds (669 upsets of 2340 games).
Upsets ARE Prevalent
For me, the most exciting aspect in NCAA tournament is seeing a top seed unexpectedly lose to a lower-seeded, under-financed, non-Power Five conference foe (except, of course, when it involves my beloved Iowa Hawkeyes). In 2024, #14 Oakland defeated #3 Kentucky on the first day of the tournament, sending John Calipari on to Arkansas. Thank you, can I have another!
Between announcing the brackets on Selection Sunday and the tournament starting on Thursday (ignoring the play-in games), on-air pundits, bracketologists, and assorted talking heads spend every waking hour talking about teams, rosters, injuries, conference strength, who’s over-seeded, who’s under-seeded, who’s hot, who’s not, travel schedule, and everything else.
The analytics spewed are mind-boggling: Well, Sarah, UMTX hasn’t won a neutral-site game against an opponent starting a former water boy wearing Adidas shoes since the Nixon presidency, so I’m picking UABW despite the seed difference.
We know that upsets occur, but have you really dug into the numbers? No? Well, let’s do it!
Regionals
The 2024 NCAA men’s tournament was the 39th men’s tournament with 64 teams in the main draw, 156 regionals * 15 games per regional = 2340 total games. The 669 upsets means that an average 4.29 upsets occur per regional.
The actual numbers of upsets per regional closely matches that: between 1985 and 2024, 35 regionals had 4 upsets (22.44%) and 41 regionals had 5 upsets (26.28%). Outliers do exist: 1985 East Regional is the only time that no upsets occurred, and two regionals had more upsets than chalk.
Final Four
Though the stakes are much higher, upsets are much less common: no upsets in 21 of 39 Final Fours (53.85%), with only 26 upsets of 117 total games (22.22%). A contributing factor is the possibility of two identical seeds playing each other, in which case no upset occurs regardless of who wins.
I’ll focus on regionals over Final Fours because regionals have 1) substantially more data (2340 vs 117 games) and 2) substantially more upsets.
Upsets By Seed
Apart from first-round matchups which are guaranteed each tournament, matchups between other seeds are not guaranteed and less common in subsequent rounds. In fact, some matchups have never occurred in any tournament: #1 v #14 or #15 seeds; #2 v #13, #14 or #16 seeds; #3 v #12, #13, or #16.
In fact, 31 matchups have been played ten or more times and 40 matchups have been played six or more times, which includes the first round.
The most-played matchups after the first round are:
- #2 v #7: 90 games;
- #4 v #5: 80 games;
- #1 v #9 / #3 v #6: 79 games;
- #1 v #4: 59 games;
- #2 v #10: 55 games;
- #3 v #11: 54 games;
- #2 v #3: 50 games played.
Aside from #1 v #4 and #2 v #3, the other matchups listed are played in the second-round.
First Round Chalk
Perhaps unsurprisingly, top-four seeds win their first round matchups almost 80% of the time: #1 @ 98.72%, #2 @ 93.59%, #3 @ 85.26%, #4 @ 78.85%. It wasn’t until 2018 that #16 defeated a #1, and it’s only occurred twice.
However, #4 through #8 winning percentages drop off noticeably, and #8 seeds lose more often than win: #5 @ 64.74%, #6 @ 60.90%, #7 @ 61.54% #8 @ 48.08%.
In the first round, 73.96% of games are won by the higher seed.
Second Round Chalk
Some definite surprises here:
- #15 seeds own #7 seeds (67% of 6 games);
- #4 v #5 is essentially a toss-up (80 games);
- #3 seeds are very vulnerable, winning 60.76% against #6 seeds (79 games) and 62.96% to #11 seeds (54 games);
- #2 seeds win 65% of the matchups with #10 seeds (55 games) and 70% against #7 seeds (90 games);
- #1 seeds own #9 seeds (92.40% of 79 games) but somewhat struggle against #8 seeds (78.67% of 75 games).
Interestingly, #9 seeds advance to the second round more than #8 seeds but then lose to #1 seeds at a higher percentage (#9 are 6-73 and #8 are 16-59 against #1 seeds).
In the second round, 71.15% of games are won by the higher seed.
Third Round
Only #1 v #12 games have no upsets (100% of 20 games), otherwise the higher seeds winning percentage drops noticeably. #4 seeds have a losing record against #8 seeds (5-6, 45.45%), and other matchups are less than 70% (#6 v #10 @ 66.67%, #6 v #7 @ 62.5%, #3 v #10 @ 69.23%).
In the third round, 69.55% of games are won by the higher seed.
Regional Finals Chalk
Trying to identify trends from Regional Finals is not likely statistically relevant, as only four matchups have occurred more than 5% of the time: #1 v #2 (48 games), #1 v #3 (27), #1 v #6 (10) and #1 v #11 (8). However, that shouldn’t stop us from trying!
Probably the most notable matchup – and largest potential bracket points – is #1 v #11, where the eight games have been easily split. The #2 and #8 favors an upset, three of five games.
In the regional finals, 55.77% of games are won by the higher seed.
Conclusions?
Truthfully nothing.
Seeding is only one variable among many that could be included deciding how to fill out your brackets: Did the pep band travel with the team? How far did the opposing team travel? How many days since the conference tournament wrapped up? How many assistant coaches does the team travel with? What injured players are going to be available? What’s the site’s temperature and altitude? Average NIL per player? Nike vs. Addidas? Coke vs. Pepsi? Did the hotel’s fire alarm go off in the middle of the night? Did the coaches daughter bring her lucky teddy bear? Uggh!
There’s a reason that perfect brackets are elusive, and that’s the beauty of it all. No opinion matters once the game starts, and that’s where the fun begins.
