OleGunnar's measure doesn't measure improvement or decline at all. If you take the +/- 33% every year, then the percentages of games in each category are going to be roughly the same. The standard deviation is important if you're a team owner concerned about staffing needs. It might also show some stability as fewer games become outliers or as the deviation shrinks but again, that measure is satisfying a completely different goal than what this thread is about. For the purposes of measuring growth and comparing years to one another, using a static number is a much better barometer.