The only major traditionally played according to the "double in, double out" format is the World Grand Prix. That, of course, has its impact on the averages, which are lower than on the other majors.
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Winner Luke Humphries had an average of 93.30 in this year's final. Had the tournament not followed the "double in, double out" format, he would have had an average of 99.70. Gerwyn Price also would have scored more than six points higher.
Below you can see a list of all the winners, calculated without starting a double.