In a recent article I presented evidence that offenses should generally pass more often on first down. Accounting for both the potential gains and the potential risks of each type of play, passing tends to lead to a greater net point advantage than does running. The analysis was based on a concept known as Expected Points, which measures the average point advantage an offense can expect given a down-distance-field position situation.
Expected Points incorporates all the various factors such as turnovers, yardage gains, sacks, incompletions, first down conversions, scoring, and so on. But I thought it would be helpful to dig deeper to investigate how and why passing appears more advantageous. In this article, I'll present a series of graphs comparing running and passing on first down, each one looking at a different facet of the game.
As in the original article, all data are restricted to what I call 'normal' football conditions, when time is not a factor and the score is relatively close. I looked at plays from the first and third quarters and when the score was within 10 points. This way, the effects of 'hurry-up' play and 'trash time' are excluded.
The first graph looks at series conversion rates. Generally, offenses that begin a series with a pass are more likely to convert than offenses that begin a series with a run. Note that this includes not only a conversion on the first down itself, but on subsequent plays on the series as well. Only inside the 10 yard line do runs tend to lead to conversions more often. Touchdowns are considered successful conversions. On all the graphs, be careful to note the scale on the vertical axis. Sometimes a small difference can look large, and vice-versa, due to the span of the scale.
The graph below looks at turnovers. Passing plays lead to a higher risk of turnover than run plays on 1st down, whether due to interception or the sack-fumble.
As always, the usual caveats apply.