In the 1980s, NBA teams won about 65% of their home games. Today it’s about 55%, and in the playoffs even the favourite’s edge in its own building has started to slip.
That much has been written about before. Two things here have not. The suspect everyone names is the three-point line, and the case for it rests on the two trends falling together over the same decades. Tested more tightly, about 42% of that lockstep turns out to be two trends drifting the same way, and a season’s three-point rate shows no sign of forecasting the next season’s change in home court beyond what home court’s own history already tells you. The three-point effect is real, but it shows up cleanly only when games are compared inside a single era, and it reaches close to half the decline, not all of it. And the biggest single piece of the decline on the stat sheet is not shooting at all. It is rebounding, which no paper or article on this subject had measured, and which this report can show clearly and cannot explain.
The long report is split here into eight shorter reads. Start at the top, or jump to the suspect you came for.
- Home Court Advantage Is Fading: the case laid out, how much home court advantage has fallen, and what has happened to the playoff favourite’s edge at home.
- The Whistle: the friendly whistle was real in every decade; watch it fade in the regular season, about half from the move to threes and the rest most likely from officiating getting fairer.
- The Three-Point Suspect: the move to the arc is the obvious culprit, so how much of the decline does it actually explain?
- The Mystery on the Glass: the biggest single piece of the decline on the stat sheet is rebounding, and it is the one the data can measure but not explain.
- The Usual Suspects: the prime suspects (travel, crowd size, pace, rest, rule changes), most with weak evidence and a possible mid-1990s dip that cannot be pinned on one rule.
- The Playoffs Are Different (and the Same): home court advantage still swings a single playoff game, but a best-of-7 leaves only about a third of that edge, and the favourite’s home edge over the underdog held for decades before narrowing in the latest seasons.
- The Altitude Holdouts: why Denver and Utah still hold the league’s biggest home edges, and home games that have grown more lopsided in both directions even as home wins shrink.
- How I Know This Isn’t Made Up: the battery of checks built to break the findings, why most held, and the ones that didn’t.
Want the receipts? The last article, How I Know This Isn’t Made Up, links every check and the full investigation, for anyone who wants to verify a claim rather than take it on faith.
- Why NBA Home Court Advantage Is Disappearing: the four questions answered in one place, if you landed here first.
- Frequently Asked Questions: quick answers to the questions readers ask most, many linking to the article behind them.
- Related Work: the wider academic and journalistic landscape, and where this report agrees, disagrees, or fills a gap.
About this series.
I’m investigating questions about the NBA that deserve deep dives, and to see what can be understood with some statistical analysis.
Every claim these articles rest on is checked against its own number automatically, and each of those checks has been made to fail on a deliberately wrong one. The numbers are Python on public NBA data anyone can re-pull. The prose is drafted with AI under my direction and verified against the analysis before it ships. Tens of hours of arguing and checking.
I’ve done everything I can think of to force it to be correct.
The numbers behind every article are the same public data: every NBA game result since the 1983-84 season, plus NBA.com’s officiating and player-tracking feeds where an article leans on them, all pulled with the open-source nba_api tool; the attendance records come from Basketball-Reference.
Figures as of the 2025-26 season.
Revised October 2026. This is the second edition of the series. The first, published in August, got several things wrong, and this version replaces it: which seed was at home in many early playoff games, and so how a weaker team fared at home in the playoffs; how much extra rest helps in the playoffs; what the mid-1990s rule changes did; what the empty arenas of 2020–21 can show about crowds; how the franchises rank on home court; and parts of the rebounding story, starting with whether fewer missed shots explain its fade.