Does Parity Improve year-to-year

This was a common question after the last post I made, so I thought I'd look into it.

I looked at the goals, D's, throw aways (ignoring throw drops), and drops from seasons 1 - 3 averaged over each player per game. What's interesting (if you like math...) about doing it this way is that I can apply the Central Limit Theorem and do statistical analyses, since the mean of the means is normally distributed. 

THE DATA!

Goals - http://imgur.com/M5qUhLy

D's -  http://imgur.com/u4KFSYz

Throw Aways -  http://imgur.com/xiEjJSF

Drops - http://imgur.com/qU6HZ5b

Passes per goal - http://imgur.com/h0X926i

THE INTERPRETATION!

What does it all mean Basil? Each dot represents the average of all players for one week. For example, Season 1, Week 1, players averaged 1.85 goals; Compare this with season 3 week 10 where the average goals per player was 1.47.

Season 1 to Season 2 shows no significant drop in goals scored per player per game. However, when we get to season 3, the goals per player drops from an average of 1.7 to 1.49, which is statistically significant. We can conclude that players are scoring less goals each from season 1 to season 3. This suggests that parity is getting worse.

Similar trends can be observed in all the stats measured; D's (0.99 -> 0.98 -> 0.74 per player per game), Throwaways (1.98 -> 1.86 -> 1.49), and Drops (0.69 -> 0.58 -> 0.42) are all on the decline. Only D's stayed consistent in the first two seasons, before declining in the third season. To me, turnovers are a good measure of "how good is the league" since they should decline as players get better, especially when related to drops which are almost always the receiver's fault. Since these metrics are declining year to year, possessions are getting hard to come by. This numbers are all significantly different (except D 1 - 2), showing a steady decline. This suggests parity is getting better since turnovers are becoming more infrequent.

The number of completions required to score a goal is also increasing. In Season 1 and Season to it took on average 7.5 and 7.45 completions to score a goal. This season that number is up to 8.17. More passes means that the defense is getting tighter and it's getting harder to score. Again, the increase from Season 2 to Season 3 is statistically significant. We can conclude that it is the defense that is forcing more passes before a score, since we already concluded that turnovers are decreasing. Therefore, this suggests that parity is getting better since the defense is getting better.

CONCLUSION!

It's easy to interpret the data and conclude what you want to conclude, but I feel that since turn overs are harder to come by and it is taking more passes to score goals that parity is getting better. Although players are on average scoring less goals, I also think this is representative of the quality of playing going up, making goals harder to come by.