It was 11 years ago that I first asked the question, why do teams run the ball? And then four years ago, I revisited that post. Today, a further update.

Let’s begin by measuring how effective teams have been, on average, at both running and passing. To measure rush efficiency, we will use Adjusted Yards per Carry, which is calculated as follows:

(Rush Yards + 11 * Rush TDs + 9 * Rush First Downs) / (Rushes)

For passing, we will use a modified version of ANY/A by also giving credit for first downs. Here’s the formula:

(Gross Pass Yards – SackYardsLost + 11 * Pass TDs + 9 * Pass First Downs – 45 * INTs) / (Pass Attempts + Sacks)

As a reminder, all touchdowns are recorded as first downs, so this formula actually provides a 20-yard bonus per touchdown on top of however many yards were gained on that scoring play. ^[1]Ideally, we would incorporate fumble data into this as well, but unfortunately, we can’t determine whether fumbles happened on rushing plays or pass plays when looking at individual or team … Continue reading

So here is the league-wide average efficiency rates for both rushing and passing since 1950. For most of the ’50s, rushing was the better way to move the ball, and while passing was more effective than rushing in the ’60s, the trend reversed in the ’70s. In 1977, teams averaged 6.01 adjusted yards per carry and 5.74 adjusted yards per pass play. Of course now things are much different: over the last 5 years, teams are averaging about 6.5 adjusted yards per rush and 8.7 yards per pass play.

I love that graph because it shows exactly how things have changed over 7 decades of NFL history. But in some ways, the next graph – which shows the same data — is even more useful. This next graph shows the pass efficiency each year divided by the sum of both rush efficiency and pass efficiency. So, for example, if the passing average was 4.0 and the rushing average was 5.0, then you would get 4/9 or 44.4%. If we keep the rushing average at 5.0, but raise the passing average to 5.0, you would get 50%; raise the passing average to 7.5, and you get 60%. If you are wondering why we are plotting it this way, you’ll see why in a moment, but here’s the graph:

So in 2018, the average passing efficiency was 8.90 per play and the rushing efficiency was 6.95 yards per play; that means the passing efficiency divided by the sum of the rushing and passing efficiency was 56%. In 1994, when rushing efficiency was really poor, the ratio was actually 57%: teams averaged 7.83 adjusted passing yards per play and 5.97 adjusted rushing yards per play.

So now we have our hands around the quality of rushing and passing, what about the quantity? This graph shows the percentage of offensive plays each year that were passing plays (i.e., pass attempts or sacks):

You might notice that those last two graphs look pretty similar. In fact, we can plot them on the same graph. Once again, the green line shows the percentage of plays that were passing plays, and the orange line shows how many adjusted yards each pass play gained divided by the average adjusted yards gained by each pass play and each run play. The two lines move in tandem, which makes perfect sense:

The biggest deviation occurs in the late ’70s, where teams just gave up on passing despite it only being somewhat worse than rushing. But otherwise, these two lines track almost perfectly, with a correlation coefficient of 0.86.