The Real Distribution of Sets at Grand Slams

Today I noticed that the last six matches at the Australian Open had all been decided in straight sets. That streak was finally broken when Shelton beat Ruud in four sets.

That got me curious, so I calculated the percentage of matches at Grand Slams that were decided in 3 sets, 4 sets, 5 sets, or by retirement.

These are the figures for the period 2010–2025:

• 3 sets: 47.2%
• 4 sets: 30.4%
• 5 sets: 18.7%
• Retirement: 3.6%

I then went a step further and broke this analysis down by tournament. And here are the results:

What stands out most is that Roland Garros has the highest share of straight-sets wins and the lowest share of five-set matches.

This can make sense: clay is the surface where there is the least room for surprises. Top players tend to dominate underdogs more clearly. One day we’ll put hard numbers on that effect.

Another notable point is that the US Open has by far the highest rate of retirements. It more than doubles the figures seen at Roland Garros and Wimbledon and is around two percentage points higher than the Australian Open. Why?

Although average temperatures during the tournament are similar in New York and Melbourne (around 20°C / 68°F), humidity is significantly higher in New York, roughly 70–75%, compared to 60–65% in Melbourne.

On top of that, and surely more important, the US Open takes place near the end of the season, when players tend to arrive in worse physical condition. These factors likely explain the higher retirement rate.

Aside from that, I don’t see anything particularly remarkable.

At some point, I’ll run this same analysis by pre-match odds levels, what can be more important from a betting perspective.

Obviously, the larger the gap between the underdog’s odds and the favorite’s odds, the higher the percentage of matches decided in straight sets and the lower the share of five-set matches.

Still, it should be interesting to see the numbers, especially when evaluating over/under sets markets.