On his last couple podcasts, Bill Simmons wonders why home court advantage doesn’t matter anymore. He listed several possible reasons, which were mostly moronic. Bill, if something impacts both the home and visiting team equally, it has no explanatory power. Obviously. Let’s look at this a bit more rigorously than he did.
Is it true?
First, is the assumption true? Is the home court advantage diminishing?
In the regular season, the home court team has gone from winning ~60%+ up to the 1990s to ~55% today. Vegas bakes in 2.5-3 points for the home team, it used to be 3-4.5.
What about the playoffs? This is harder to figure because home court is given to the better team. But here again we’ve gone from ~65% to ~58%, and Vegas bakes in 2.5-3 points, though it varies heavily on context.
Conclusion: Yes, the assumption is true.
Do we know why?
Since the phenomena is true, the next step is to see if we already know why it happened. The answer is yes. It’s been studied and known for decades that the home court advantage comes primarily from unconscious referee bias. They don’t mean to, they don’t want to, but referees are human and react to the fans yelling. One of the ways we can see this is how home court advantage completely disappeared in the bubble.
If home court advantage comes from referee bias, has it changed? Yes it has, and that is the answer. Refereeing has become increasingly professionalized. Modern refereeing is heavily scrutinized, graded by micro-cameras, subjected to centralized NBA replay center, play-by-play reports of the last two minutes, increasing social attention, etc. The days of cowboy referees are long over. For all the jokes about Scott Foster, individual referees just don’t impact a game like they used to.
There you go, that’s the answer.
Other factors:
Three-point shooting: The rise of three point shooting increases scores for both teams, but more importantly increases the variance in the outcomes. Increased variance eats away at the home court advantage. Think of an exaggerated case – let’s say at the end of each game, each team takes one shot. If the shot goes in, they get 100 points. In this imagined scenario, the variance would be enormous, swamping everything else that goes on in the game. (It’s analogous to Quidditch, where the optimum strategy is to ignore everything except getting the Snitch. Everyone on the team should be a seeker.) Note that in the last five years of playoffs the Boston Celtics (who shoot 3-pointers aggressively) have a win-loss percentage 10 points higher when playing on the road than at home.
Easier travel: Every team has chartered flights, most have team planes built especially for their comfort. They stay in nicer hotels. The NBA has reduced the number of back to back games. All of this means that the visitors are in much better shape than they used to be. This also applies to the bubble year control case, so there’s some conflating variables there.
