Harvard economist John Kenneth Galbraith is credited with coining the term “conventional wisdom” in 1958 in his book The Affluent Society. The term has come to represent ideas that are commonplace beliefs that are acceptable and comfortable to society. The consequence of that acceptance and comfort allows conventional wisdom to be highly resistant to facts that contradict the conventional wisdom. For example: the past belief that world was flat.
When it comes to the NFL, conventional wisdom states that it’s a passing league. Observe:
“This is still a passing league.” – Mark Craig, The Star Tribune
“The NFL’s transformation into a passing league…” – Bucky Brook, NFL.com
“The NFL is a passing league.” – Michael David Smith, Pro Football Talk
“The NFL is a passing league.” – Trent Dilfer, ESPN (former Baltimore Ravens QB)
“The NFL is a passing league.” – Pat Kirwan, NFL.com
“It is a passing league.” – John Harbaugh, Baltimore Ravens head coach
“It ‘s a passing league.” – Solomon Wilcots, NFL Network and CBS Analyst
“It ‘s a passing league.” – Bill Cowher, former Pittsburgh Steelers head coach
“Obviously, the NFL is more of a passing league now…” – MJD, Shutdown Corner
“…the NFL is a passing league.” – Ryan Wilson, Fantasy Sports Portal
“This is a passing league…” – National Football Authority
It has become easy, comfortable, and acceptable to blindly state that the NFL is a passing league and consider that statement as fact…i.e. it’s become conventional wisdom. However, regarding the subject of conventional wisdom, Steve Albini, Noam Chomsky, and Peter Jennings are just a few that have urged caution in accepting conventional wisdom without applying a test or some skepticism:
“Doubt the conventional wisdom unless you can verify it with reason and experiment.” – Steve Albini, music producer (produced Nirvana’s “In Utero”)
“Either you repeat the same conventional doctrines everybody is saying, or else you say something true, and it will sound like it’s from Neptune.” – Noam Chomsky, philosopher, linguist, cognitive scientist, activist
“I’ve always shied away from conventional wisdom, though I know the power of it.” – Peter Jennings, former ABC News anchor
I’m going to step up and be skeptical. What does it even mean to be a “passing league?” Is the NFL really a passing league? And, why would it be true or false?
First, to determine if the NFL is or isn’t a passing league, I’ll define “passing league.” There are actual football leagues that are true passing leagues…they play 7-on-7 scrimmages with a quarterback, two running backs, two wide receivers, a tight end, and a center and they predominantly work on passing drills with the offensive skill position players only. Basically, there’s no running game involved. Obviously, the NFL doesn’t meet this definition since there are linemen other than the center (tackles and guards) and the running back actually carries the ball periodically. But the premise behind saying “the NFL is a passing league” implies that greater importance has been placed on the passing game at the detriment to the running game. Therefore, “passing league” in reference to the NFL will be defined as the philosophy held that passing is more important than running in pursuit of success and winning in the NFL.
Now that our verbiage is established, we’ve got to answer whether more importance has been placed on passing and how that has affected rushing. In the upcoming analysis, I went back to 1983 and gathered offensive statistics for each season. It’s important to note that the NFL has expanded from 28 teams to 32 teams since 1983. So, to account for these changes, the season offensive data was transformed into per team per game data to allow for direct comparisons between seasons. For full disclosure, here’s all the data I used (click on the tables to view them at full size):
The first thing we need to look at is the breakdown of the offensive plays since 1983. Looking at Chart 1, you might notice a variation between the number of total plays and the sum of the passing plays and running plays. This difference is due to sacks. The database I used included passing attempts, rushing attempts, and sacks each as its own unique type of offensive play and sacks seemed to account for between 2 and 3 “offensive plays” per team per game each season.
It’s evident that the number of offensive plays the average team runs hasn’t changed much since 1983. There have been dips and jumps, but the number of offensive plays generally hovers around 63 for each team each game. When looking at the breakdown between how many of these offensive plays were runs versus passes, a trend manifests: the number of pass plays seems to be increasing while the number of run plays seems to be decreasing. (The trend lines represent the linear approximation over the time period.)
To take a closer look at this divergence, I charted the difference to observe how much the gulf between pass plays and run plays is growing per year.
It’s fairly obvious that when subtracting the number of run plays from the number of pass plays, not only is the number positive every year except 1983, but the number increases significantly (to smooth out the line a little bit, I showed a 5-year moving average as well).
Since the total number of plays is not changing much but the number of pass plays is increasing while the number of run plays is decreasing, it’s obvious the NFL is collectively moving towards a pass-dominant game strategy. By this measure, we can conclude that greater importance has indeed been placed on the passing game and it comes at the detriment of the running game. This meets our definition of a “passing league.”
Ok, so the NFL is a passing league. Why?
We can look at this a few ways. The immediate goal of an offensive play is to gain yards. The ultimate goal of an offensive drive is to score points. Chart 3 shows the breakdown between total yards gained per team per game and how many of those yards were earned through passing and rushing plays.
From Charts 1 and 2 above, we know that teams are increasingly favoring the pass over the rush. So, it’s no surprise that passing yards have increased slightly since 1983 while rushing yards have decreased slightly. While year-to-year change in yards doesn’t tell the story, the risk-reward relationships just might. Take a look at the yards gained through passing…even in the mid-80s teams were compiling approximately 75 more yards through the air than they did on the ground, and that’s back when there was a greater collective balance between passing and rushing plays. Continue through the time period, and teams are now amassing 100 more yards throwing than running. There’s a greater immediate reward that can be expected when calling a passing play versus calling a running play.
Yards don’t win games though; points do.
Chart 4 tells a similar story as Chart 3 — more passing plays should result in more scoring than running plays since a touchdown is worth the same amount regardless of the vehicle chosen to break the plane of the goal. Still though, we can see that passing has always resulted in greater point production than running, even when the pass:rush ratio was more balanced in the mid-80s.
Charts 3 and 4 show us the consequence of choosing a passing play over a running play, greater expectations for yards gained and points scored. However, that’s been the case the entire time period from the 1983 season through the 2011 season. This constant does not lead me to conclude that we’ve figured out why the NFL has become a pass-favoring league. We need to isolate the pass statistics and see what we can find there.
The first success of a passing play is a catch. We’ve established that the number of passing plays has increased per team per game. If we look at the successfulness of these plays, we see that not only are completions increasing, completion percentage is also increasing. (The number of passing plays and the completions and incompletions are showin the the chart as numbers. Since completion percentage ranged from 53% to 62%, I was able to show that line on this chart even though the unit for each data point is percentage, not a counted number.)
We’re beginning to see a picture here: passing plays result in greater yards gained and more points scored than running plays by default, and teams are actually becoming increasingly efficient at throwing the ball. These trends obviously place more value on a pass play than a running play.
I’m still bothered, however, because using completion percentage to observe greater efficiency in the passing game does not have a comparable metric in the running game since a dropped handoff is a fumble whereas a dropped pass is a dead ball. If I had additional data on running plays that broke out the yards gained into segments such as negative yards, 0-3 yards gained, 4-6 yards gained, etc., I could probably come up with an efficiency metric for rushing plays, but I don’t have access to that kind of database.
Instead, I think we can compare passing and running in an Expected Return format since the two types of plays share some similar characteristics: touchdowns are worth 6 points for both, each has a turnover threat (interceptions and fumbles), and those turnovers can lead immediately to opponent touchdowns. Expected return on an investment is the difference between the historical return and the risk. We can estimate both of these values for passing and rushing. Since the only common comparable I have available is touchdowns, I can look at the the touchdowns per pass attempt and touchdowns per rush attempt to determine the historical return. For risk, I can look at touchdowns per interception and touchdowns per fumble. The difference will be the Expected Return on the investment of choosing to pass or run.
To explain the method a little further, an action has a potential consequence and that consequence has a cost. The product of the probability of the consequence and the cost of the consequence is the return if it’s favorable or it’s the risk if it’s unfavorable. Let’s look at the Expected Return for investing in a run play first.
The trendline for the Expected Return is 0.0014x + 0.15. The slope 0.0014 represents theyear-to-year change in the rushing Expected Return…i.e. a team can expect to score 0.0014 more points per rush this year than they could have expected last year. Solving for the rushing Expected Return in 2012 would be 0.0014*(2012-1993) + 0.15 = 0.1766. A team can expect to score 0.1766 points every run play.
Let’s look at the same scenario for passing.
The trendline for the Expected Return is 0.0014x + 0.21. Again, the slope of 0.0014 represents theyear-to-year change in the passing Expected Return. The fact that the slope for rushing Expected Return is equivalent to the slope for passing Expected Return tells me that teams can expect the same growth rate for scoring each new season regardless of choosing to pass or rush on an individual play. However, solving for the passing Expected Return in 2012 would be 0.0014*(2012-1993) + 0.21 = 0.2366. A team can expect to score 0.2366 points every pass play.
Using this Expected Return analysis, choosing to pass yields a team 0.06 more points than choosing to run. That may not sound like a lot, especially since touchdowns are rewarded in 6-point increments, not 0.06-point increments. But, when comparing the choice to pass to the choice to run and measuring the Expected Returns, passing yields a 34% greater chance of scoring than running.
So, we’ve defined and proven that the NFL is a passing league, and we’ve figured out why a coach would choose to pass more often than run. Of course, the choice to run or pass is not simply an isolated decision that based on reward vs. risk; it’s situational. It would be unfair and too generalized to present the above data and leave it at that. Coaches balance the choice to run or pass on multiple factors including the opponent’s defensive strengths and weaknesses, game strategy (milking clock, etc.), and offensive strengths and weaknesses. Additionally, when looking at the league as a whole like I did, it would be unfair to not step back and realize that we’re talking about a spread of only 6-7 more passing plays per team per game than running plays (Charts 1 and 2). That’s still relatively balanced considering there’s an average of 63 offensive plays per game. Assuming that number of total offensive plays stayed the same, the average team in the average game would only need to call 3 more running plays than passing plays and they’re back to almost perfect balance. Still though, it has been shown that the trend is increasing for passing plays at the expense of running plays AND passing plays offer greater reward with decreased risk. I find it reasonable to conclude that the NFL increasingly prefers the pass over the run.
Ultimately, beyond reward and risk, what is driving this trend though? It’s the constantly changing rules and their benefit to the offense. I looked at the rule changes from 1981 through 2011 and highlighted what I think are rules that benefit the defense and rules that benefit the offense. You may have noticed that Charts 6 and 7 began at 1993 whereas the previous charts began at 1983. The reason for this shift is that 1993 is the point where the season-to-season rule changes started heavily favoring the offense. Also, I looked at rule changes as far back as 1981 because I wanted to allow a few years for teams to adequately incorporate the rule changes.
For the 1981 through 1992 period, I tallied 5 rule changes that benefitted the offense and 5 rule changes that benefitted the defenses. From 1993 through 2011, I counted 19 rule changes that benefitted offenses and only 9 that benefitted defenses. It’s obvious that the NFL as a collective organization values offense greater than defense.
With a leage that values offense moreso than defense coupled with teams that value passing more than rushing, it’s no wonder the NFL has become a passing league.
Here’s the rule changes table if you’re interested (it’s really long, so click on it to view at full size). The yellow boxes are rules I deemed beneficial to the defenses and the blue boxes are ones I saw as beneficial to offenses.