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Yesterday, I wrote how the NBA seemed to undervalue the three-point shot for many years. While the 3-point shot was consistently the better EV play, and the ratio of three-point shots to overall shots was increasing, it didn’t seem to increase quickly enough. As pointed out in the comments, one could make a pretty similar claim about pass/run ratio in the NFL.

It’s a little misleading to start things in 1970, since that’s really the beginning of the dead air era in football history. Pass efficiency was very high in the late ’40s and parts of the ’60s, so a chart beginning in 1970 would inaccurately imply a linear progression of the passing game. That said, because first down data is spotty the farther back we go, and because of the complexity involved in deciding how to treat the AFL, I’m going to limit myself today to the period from 1970 to 2016.

To measure pass efficiency, I used a familiar model: yards per pass attempt, including sacks, with a 9-yard bonus for first downs, a 20-yard bonus for passing touchdowns (excluding first downs), and a 45-yard penalty for interceptions; in other words, ANY/A with a first down bonus. For rushing, I used yards per carry, with the 9/20 yard bonuses for first downs and touchdowns. As you can see, in the early ’70s, a close to 50/50 split was pretty defensible.

pass rush eff 1970 2016

It’s also remarkable how much the passing game has increased in recent times; the jump in passing game efficiency from 1978 to 2003 is roughly the same as from 2013 to 2015. Meanwhile, the graph below shows the pass ratio (i.e., sacks plus pass attempts divided by total plays) in each year since 1970:

pass ratio 1970 2016

We a similar change in pass ratio, but I don’t think any member of the football analytics community would tell you that it is commensurate with the increase in pass efficiency. There is a natural tendency for the best passing teams to pass less frequently due to the Game Script, so there is likely some sort of cap on high high the league-average — or any great passing team — will get in this regard. But 2016 saw the pass ratio jump to 59.1%, and there’s little doubt that the 60% mark will fall sometime soon, too.

  • LightsOut85

    You probably wouldn’t get as large of a sample (/as far in the past), but it’d be interesting to see the efficiency of run v. pass when it’s adjusted (to at least some degree) for game script. Run eff. probably wouldn’t change much, but perhaps certain game situations would show a lower pass eff., (somewhat) closer to that of runs.

  • bubba29

    are there any metrics that take into account offensively beneficial penalties during pass plays? as a former db i may be hypersensitive to the idea that many pass plays end up resulting in a penalty against the defense that usually results in a first down. also, looking at your chart here, what changed around 1977 that spiked passing efficiency?

    • Josh Sanford

      From Wiki: The league passed major rule changes to encourage offensive scoring.[2] In 1977 – the last year of the so-called “Dead Ball Era” – teams scored an average of 17.2 points per game, the lowest total since 1942.[3]

      To open up the passing game, defenders are permitted to make contact with receivers only to a point of five yards beyond the line of scrimmage. This applies only to the time before the ball is thrown, at which point any contact is pass interference. Previously, contact was allowed anywhere on the field. This is usually referred to as the “Mel Blount Rule”

      The offensive team may only make one forward pass during a play from scrimmage, but only if the ball does not cross the line and return behind the line prior to the pass.

      Double touching of a forward pass is legal, but batting a pass towards the opponent’s end zone is illegal. Previously, a second offensive player could not legally catch a deflected pass unless a defensive player had touched it. This is usually referred to as the “Mel Renfro Rule”. During a play in Super Bowl V, Baltimore Colts receiver Eddie Hinton tipped a pass intended for him. Renfro, the Cowboys defensive back, made a stab at the ball and it was ruled that he tipped it ever so slightly (which he denied) into the arms of Colts tight end John Mackey, who ran for a touchdown. Later, this rule was also the one in question during the Immaculate Reception in 1972. But despite these two incidents, the rule change did not occur until this season.

      The pass blocking rules were extended to permit extended arms and open hands.

      The penalty for intentional grounding is reduced from a loss of down and 15 yards to a loss of down and 10 yards from the previous spot (or at the spot of the foul if the spot is 10 yards or more behind the line of scrimmage). If the passer commits the foul in his own end zone, the defense scores a safety.

      Hurdling is no longer a foul.

      A seventh official, the Side Judge, is added to the officiating crew to help rule on legalities downfield.[2] The addition of 15 officials (one per crew) forced three-digit numbers to be used for the first time.

    • Quinton
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  • Phil

    I looked into this a while back, with I believe the 2003 data

    and there was a slight negative correlation between run pass ratio and yards per pass attempt (ie, teams that ran the ball at a higher ratio, were more effective gaining passing yards per attempt)

    seemed like there might be 2 directions of causality,

    1) teams that threw the ball more effectively got leads, and ran the ball more to end the game

    and/or

    2) game theory wise, teams that ran the ball more, got the defenses to play the run more, and thus were more effective throwing the ball
    ——————–
    I didn’t look into it with a enough detail to tease out either explanation

    I also haven’t looked into it since then, so its possible with more data the effect disappeared