Nail-Biting Index: A data-driven measure of tennis match drama

We often fall victim to recency bias— thinking every new five-setter is "the greatest match ever." The Nail-Biting Index is here that gets into match statistics to measure the drama.

Rank Match Tournament Round Score NBI Drama Tags

The NBI Formula

NBI = 0.25 × (Set Closeness) + 0.22 × (Comeback Factor) + 0.18 × (Lead Changes) + 0.12 × (Tiebreak Count) + 0.10 × (Match Duration) + 0.07 × (Break Point Drama) + 0.06 × (Final Set Tiebreak)

Set Closeness

Measures how close each set was—smaller average margins mean tighter, more competitive sets.

25%

Comeback Factor

Rewards matches where a player comes back from a significant deficit, especially from two sets down.

22%

Lead Changes

Counts how often the match momentum shifted, showing back-and-forth battles.

18%

Tiebreak Count

Number of sets decided by a tiebreak, highlighting high-pressure moments.

12%

Match Duration

Normalizes match length per set—longer, drawn-out battles score higher.

10%

Break Point Drama

Reflects the share of break points saved, emphasizing clutch play under pressure.

7%

Final Set Tiebreak

Indicates if the match was decided by a tiebreak in the final set.

6%