I first noticed that the small difference between average and good in terms of baseball batting average. 150 for 600 is .250, an average hitter. 180 for 600 is .300, a good hitter. The difference is only 30 hits over the course of a season, or about 1 per week. So getting just 1 hit more per week is the difference between being average and good. Similarly, as you say the difference between being average and good in terms of completion percentage is about 24 passes per season, or about 1.5 to 2 per game. Sounds small. But I guess it adds up and matters.