"Madison" Bucks and "Providence" Celtics: How NBA history explains home court advantage

The overriding story of this NBA playoff season has been the dramatic advantage the home team has held in nearly every contest. But what exactly explains it?

Celtics fan John Swansburg addresses that very question in a recent posting on Slate.com. After implying that the question might have no answer, he cites the four most plausible explanantions:

1. Its the building

2. Its the crowd

3. Its the refs

4. Its the travel

Ironically, had I written this post about six months ago, I would have argued vehemently that the answer had to be either (1) or (4), or a combination of both. But after researching the issue on this fabulous statistical resource site, I am now absolutely convinced by historical evidence that it is neither (1) nor (4). It almost certainly has to be (2), and probably also (3) being impacted by (2).

The NBA's forgotten "Neutral Site" Era

Those who know NBA history will remember what I call the "neutral site" schedule era. It spanned the early years of NBA history and ended following the 1973-74 season. I'm sure it served to nationalize the game in the days when the game was extremely limited in its geographic reach.

For whatever reason it existed, its peculiarity and inconsistent application provides valuable insight into the causes of the homecourt advantage in basketball. If you study the era carefully, you will find clear evidence that partisan crowds, as determined by geographic proximity to the team's home city, produced win advantages quite similar to those acheived at each teams home arena.

Of "Madison" Bucks and "Providence" Celtics

Look at this chart I made. It illustrates the impact of crowd partisanship on game results. The chart breaks down the records of 4 teams across different seasons: the Boston Celtics, Milwaukee Bucks, KC/Omaha Kings, and the Houston Rockets. Each of those teams had identifiable "semi-home" games on their schedules during the seasons sited (most obviously Kansas City/Omaha -- the only team in NBA history with two acknowledged "homes"). As you will notice, each of the team's "semi-home" records over the given timeframes significantly exceed their overall records and practically mirror their home records.

You will notice I also cited a fifth team without any "semi-home" record. From 1960-1969, the Los Angeles Lakers played a "pure" neutral site schedule. By that I mean, none of their neutral site games were played anywhere near Los Angeles or the opponents home city. And as you will notice, their neutral site record over that time parallels precisely their overall record, indicating neither an advantage nor a disadvantage in any of their neutral site outcomes.

All of which would tend to eliminate (1) and (4) as plausible explanations. The teams that played "semi-home" games played so few of them that the "semi-home" arenas were no more familiar to them than they were to they were to their opponents. So (1) can't be true. And, all four teams had to travel to their "semi-home" destinations (two of them out-of-state) and that had no adverse effect.

CONCLUSION

The home court advantage in basketball is very significant and very real. And it is almost certainly a product of crowd partisanship. How the partisanship actually manifests itself, I cannot say.

But the explanation is almost certainly psychological. Anyone who has performed in an indoor spectator sport and has "felt" the roar of a partisan crowd... or the baying of a hostile mob... will concur that the first can be unbelievably uplifting, and the second quite disconcerting. And your concentration, your effort, and even your "comfort" level is effected accordingly. (The same, I believe, impacts the judgment of the referees -- its human nature). And in basketball, all of those things combine to dramatically tilt the advantage to the home team.

Stay tuned for my future post, which builds on this post and asks the following question: "How much home court advantage did the Bucks leave at the old Milwaukee Arena?" Hint: What year did Bucks history take a turn for the worst? What event occured the year before?