Home Field Advantage is Diminishing in Most Leagues, Except One

Much research has been done on the extent to which home field advantage exists (it does, in some cases by a lot), and also why - Scorecasting determined referees are the primary driver, subconsciously tilting calls in favor of the home team.

The main hypothesis there though is that its the subconscious effect of rabid fans that influence the refs' calls - and this effect will presumably disappear with games coming back at neutral sites, without fans.

But how much will this matter? It's been a known effect in the NBA that improved travel and other technological perks have caused home court to decline in recent years - so will teams that have earned home court all season long (like the Lakers and Bucks) really be losing as much as they used to with no fans attending games?



NBA and NHL have seen declining HFA in recent seasons, with NBA having a very pronounced effect. Home court/home ice still exists, but to a lesser magnitude than it used to.


NFL and MLB have seen an even sharper decline, with each most recent season actually dipping to right at/below 0 - meaning home field advantage didn't exist last season.

Which leaves one domestic US-based league that has been bucking this trend, and actually is higher than its counterparts in other countries:

"What are the odds?" UNC's 94 Year Win Streak Over Clemson At Home

I've been meaning to write this post for years, so it's fitting I only get to it only after college sports' most absurd streak is over.

North Carolina beat Clemson 59 consecutive times in Chapel Hill, the longest such streak in NCAAB, dating back to 1926. Admittedly, the annual component became less impressive once Miami and Va Tech joined the conference in 2004 and we stopped playing Clemson at home every year. But beating ANYONE 59 times in a row is impressive, regardless of the gulf between two programs. Even throughout fluctuations in UNC's strength (we beat them by 18 at home in the worst year (2001-02) in the program's history), the streak persisted until this year. 

So just how unlikely was it? Short of calculating every team's RPI (a notoriously unreliable metric) back to 1926, I tried to approximate it through a few different methodologies.

If the talent disparity each year was equal to 2005's title team (21 points better than Clemson), each win would have a 97% chance: 0.97 ^ 59 = 16.6%, or about 1 in 6. Not that crazy.

Taking the other extreme, if every year was equal to the 2002 team, where Clemson actually was slightly BETTER, factoring in home court would yield a 63.94% win probability: 0.6394 ^ 59 = 0.0000000003%, or 1 in 288,014,740,777. That's 288 billion. This is pretty close to each team being evenly matched and adding ~5 points for home court (65% win probability in each game). Which isn't a particularly satisfying answer either: this isn't representative of reality.

Over the full head-to-head records (home/away/neutral), Carolina led 128-20 (86.5%) going in to this season's game. Using this win probability gives: 0.865 ^ 59 = 0.019%, or 1 in 5,249.

Method	Single Game Prob	Streak Prob	1 in...
Worst KenPom	63.94%	0.0000000003%	288,014,740,777
Even w/ HFA	65.04%	0.0000000009%	105,280,654,806
All-Time Win %	86.49%	0.019%	5,249
Best KenPom	97.00%	16.58%	6

Even so, this streak had a 0.9% chance of ending (1 in 111) late on January 11 - until that unlikely event happened too.

NBA (Reported) Player Heights Did Significantly Change This Offseason

This information may be past the zeitgeist, but at the beginning of this season the NBA cracked down on incorrect roster information, including players' heights to ensure “the integrity of information” (see: gambling!; although my favorite player on my favorite team had something to do with it when Buddy Hield announced his age had been off by a year for his entire professional career). 

53 players' heights changed, which isn't an insignificant amount - it represents about 11% of the number of rostered players. While it's possible some of players legitimately grew (Giannis famously grew 2 inches since he was drafted), most teams/players were simply fudging their heights.

Of these 53 changes, 46 of them were negative (87%), i.e. the player's height decreased. Of these declines, the max was Hayward Highsmith dropping 3 inches, although the most common reduction was 1 inch (29 players, or 63% of the height drops).

Of the 7 players to "grow" (13%), one notable increase was Kevin Durant, who some speculated might go up 2 to 3 inches - according to the Brooklyn Nets, he only increased by 1 inch (no player's height went up by more than an inch).

3 players (6%) had their height cross a foot threshold, i.e. falling from 7'0" to 6'11": Joel Embiid, JJ Barea, and Carsen Edwards.

Disclaimer: While William Hill is the official sports betting partner of the NBA, I implore you to go literally anywhere else - they're notably the worst book for sharps