In some ways, the premise of this post is geeky even for this site. And that’s saying something. There is a debate over the proper way to measure league average. For example, when we say the average completion percentage in the NFL is 61.2%, this is generally assumed to reflect the fact that in 2013, there were 18,136 passes thrown in the NFL, and 11,102 of them were completed.
An alternative method of measuring completion percentage in the NFL is take the average completion percentage of each of the 32 teams. That number won’t be very different, but it won’t be identical, either. The difference, of course, is that this method places the same weight on each team’s passing attack when determining the league average. The former, more common method, means that the Cleveland Browns make up 3.755% of all NFL pass attempts and the San Francisco 49ers are responsible for only 2.299% of the league-average passing numbers. The latter method puts all teams at 3.125% of NFL average.
Wow, Chase, is this really a football blog? Two paragraphs on calculating the average in a data set? Believe it or not, that background presents an interesting way to look at how the NFL has become more of a passing league.
For example, let’s look at the 1972 season. Miami led the NFL in points scored and in rushing attempts, while ranking 24th out of 26 teams in pass attempts. Does this mean the Dolphins weren’t a good passing team? Of course not; in fact, Miami had the highest Adjusted Net Yards per Attempt average of any team that season! That year,only two teams threw over 400 passes: New England and New Orleans. And both teams were below-average in ANY/A, with the Patriots ranking in the bottom three.
In 1972, the average pass in the NFL gained 4.28 Adjusted Net Yards. But an average of each team’s ANY/A average was 4.34, because good passing teams like Miami and Washington passed less frequently than bad passing teams like New England and New Orleans. The league-wide average was only 98.5% of the “average of the averages” average; whenever that number is less than 100%, we can conclude that the better passing teams are passing less frequently.
Fast forward 39 years. In 2011, three teams topped the 600-attempt mark: Detroit, New Orleans, and New England. Tom Brady’s Patriots and Drew Brees’ Saints ranked in the top three in ANY/A (and the Lions in the top 7), while Aaron Rodgers’ top-ranked Packers in ANY/A still finished above average in pass attempts. The Tim Tebow Broncos were last in pass attempts, and in the bottom ten in ANY/A. The Jaguars, who finished last in ANY/A by a large margin, were in the bottom five in pass attempts, too, as Maurice Jones-Drew led the league in rushing. In 2011, the league-wide average ANY/A was 5.90, while the “average of the 32 teams” ANY/A was 5.85; that’s because the best passing teams were throwing more frequently than the worst passing teams (the ratio here was 100.8%).
The graph below shows the ratio of “average of each team’s ANY/A” relative to “league average ANY/A” for each year from 1970 to 2013. Remember, a percentage below 100 indicates more passes from inferior teams, while a percentage above 100 indicates the better passing teams are passing the most:
Note that the scale is from 97.5% to 102.5%; as you can quickly see, most of the action takes place in the bottom half of the graph. That is as good a picture as any to show why for quarterbacks, rate stats matter more than gross stats. Poor passing is part of a positive feedback loop for gross pass attempts: bad pass efficiency early in a game leads to a large number of pass attempts later in the game, and vice versa. And for nearly all of the ’70s, bad passing teams tended to throw more passes than good passing teams.
As you can see, though, the ratio has been on the rise over the past 44 years (the black line is a best-fit linear trend line). But the effect is not enormous, and we see this in 2013. While Peyton Manning had an incredible season, the Broncos finished six pass attempts behind the Browns, who finished 22nd in ANY/A. Russell Wilson didn’t throw very often, but Seattle ranked 5th in ANY/A while ranking 31st in pass attempts. The 49ers and Colin Kaepernick were 7th in ANY/A and last in pass attempts. Nick Foles led the NFL in ANY/A, but the Eagles ranked 27th in pass attempts. In that sense, 2013 wasn’t that out of whack with historical numbers.
Still, the general trend is clear. Two years ago, I wrote that the correlation between NY/A and pass attempts was on the rise; of course, at the time, the 2011 season looked like a new peak that was part of an ever rising standard. But over the past two seasons, that trend has curtailed a bit. Teams like Seattle and San Francisco are efficient at passing but aren’t pass-happy, which is why they seem like “throwbacks.” And Houston, despite finishing 5th from the bottom in ANY/A, was fifth in dropbacks. That’s because the Texans were the worst team in football, of course, but it also means many better passing teams chose to allow the game script to shift towards the run.