The darts market is thinner than it looks
Averages are quoted everywhere and predict less than people assume, because a leg is won by finishing and finishing is a different skill from scoring.
Every darts broadcast quotes the three dart average, and it is genuinely informative. It is also the reason a lot of darts modelling is worse than it looks, because it measures one of the two things that decide a leg.
Scoring and finishing are different skills
An average is dominated by scoring: how often a player hits treble twenty and how consistently. Finishing is a separate ability, exercised from a different part of the board, under different pressure, with a different failure mode.
Two players averaging 98 with checkout percentages of 45% and 33% are not close to equally matched. The second one leaves more legs on the table, and over a best of eleven that difference compounds in the same way a tennis serve edge compounds through the scoring system.
The variance is higher than the numbers suggest
Averages are stable and results are not. A player can average 105 and lose, because scoring heavily in legs you lose inflates the average without winning anything. That decoupling is why darts results look more random than the statistics behind them, and why a model built on averages will be confidently wrong at a rate that surprises its author.
Where the board goes loose
Leg handicaps, most of the time. They are usually derived from the match price rather than modelled from a leg-level distribution, and in a format where the number of legs is small and the variance per leg is large, a derived handicap is a coarse approximation.
What this does not tell you
How a player performs on stage against how they perform in a floor event. The gap is real, widely discussed, and supported by much less data than the discussion implies, since the two are played under conditions that differ in several ways at once.
Common questions
Is a three dart average a good predictor in darts?
It is the best single number available and it is incomplete. Scoring and checking out are related but distinct skills, and averages weight the first heavily.
Why do checkout percentages matter so much?
Because a leg is not won by scoring, it is won by finishing. Two players with identical averages and different checkout rates are not equally likely to win.
Are darts handicap markets well priced?
The main match markets are. Leg handicaps are frequently derived from them, and a derived handicap in a format this variable is a rough approximation.