Part 3 of a series on the NBA’s fading home court advantage; start with Home Court Advantage Is Fading.
Put the two trends on one chart and the case looks solved: threes climbed while home wins fell. In the mid-1980s, threes were fewer than 7% of NBA shots. Today they are about 40%. Over the same decades the home team’s regular-season win rate fell from about 65% to 55%. That makes the three-point revolution an obvious suspect, but the chart alone cannot tell us what caused what. The rise in threes accounts for close to half the decline, through shooting, foul calls, and turnovers.
The decline shows up in the four factors that make up home court advantage in the first place: shooting, rebounding, turnovers, and fouls. The rise in threes shows up in three of them.
| Factor | Share of the decline | What the rise in threes explains | How to read it |
|---|---|---|---|
| Shooting (eFG%) | ~21% | All of it | Fully explained by threes. Compare games at the same three-point rate and no separate shooting story is left |
| Fouls and free throws | ~18% | About half; the rest is a home foul edge that mostly faded over the decades | Mixed. The three-point half is measured directly; the foul edge measurably shrank, but fairer officiating is my interpretation, not a measurement |
| Turnovers | ~27% | About half; across the record the gap also closed partly on the road side, road teams’ extra turnovers per 100 possessions falling from 0.85 to 0.13 | Mixed. The three-point half is measured directly; the road-side closure is measured too, but why road teams improved isn’t |
| Rebounding | ~30% | Almost none; the home offensive-rebound rate fell farther than the away rate for some other reason | Still unknown: why the home edge on missed shots shrank |
Rebounding is the largest single factor, but threes explain almost none of its decline. The Glass and the Turnover Gap follows that missing explanation.
Why the long-run chart isn’t enough
Training, scouting, rules, and players changed alongside three-point shooting. The mirror-image lines make threes a suspect, but they cannot show that one change caused the other.
A stronger comparison looks at high-three-point games and low-three-point games from the same period. In the regular season, every 10-point rise in the share of shots taken from three goes with about 2 fewer home wins per 100 games; the playoff comparison points the same way at about 3 fewer. This means a smaller home advantage in higher-three-point games, not that home teams generally became underdogs.
That comparison strengthens the link without proving cause. The close-to-half estimate comes from looking at how the shooting, foul, and turnover edges changed among games with similar three-point rates; the investigation carries the detailed checks.
📊 Games binned by 3PA rate within each period, not across the full 40 years, one line per…
How one change shows up in three factors
The rise in threes reshaped shot selection, not just shooting percentages. The story starts in the paint. Away teams have closed the gap in paint attempts: in the late 1990s home teams generated about 1.3 percentage points more of their attempts from close range than road teams; in the most recent seasons that gap has shrunk to 0.2 points. A paint shot is more efficient than a mid-range jumper, so home teams once started each possession with a small built-in scoring advantage; that gap narrowed steadily as the three-point share climbed, the same pattern as the shooting edge. In games with similar three-point rates the home shooting advantage shows no decline at all. The closing paint gap plausibly reflects the same rise in three-point volume rather than a separate cause, though, unlike the shooting gap, no same-three-point-rate test checks it directly. In the playoffs the paint gap narrowed in the late 2010s but has since rebounded toward its old level, making this a regular-season story for now.
📊 Shot zone differentials (home minus road) over time, regular season vs. playoffs. Four…
The foul and turnover links are less direct. Three-point attempts may bring fewer drives, fouls, and live-ball turnovers, but the box score cannot confirm those mechanisms. It does show that the rise in threes accounts for about half of each fading edge.
📊 Home minus away differentials over time: free throw attempts per game (the whistle’s…
The playoffs have too few games for the same factor-by-factor verdict; only the rebounding decline is clear there. The chart below puts the regular-season result in one picture.
📊 How much each factor’s home edge declined in the regular season, drawn as one bar whose…
An independent check
Sparkle Technologies’ analysis also names the three-point revolution as a leading cause, largely from the two long-run trends moving in opposite directions. My same-period comparison still finds a link. Removing the shared drift through time reduces the long-run association by about 42%. Sparkle does not measure the lost home rebounding edge, which threes barely explain. That is why threes close only part of this case.
The lost rebounding edge is the next article’s question.
Next: The Glass and the Turnover Gap. The data show the home team’s rebounding edge almost disappeared; why it did is still open.
Back to the series hub: The Disappearing Home-Court Advantage
Data: NBA.com Stats, pulled with the open-source nba_api tool; attendance records from Basketball-Reference.