Pro-Football Reference Blog:
You’ve probably never thought about this before, but how many yards do you think the average QB gets on his median pass attempt? The answer is zero, and for most of NFL history, it was less than that. 2008 was the greatest passing season of all time (by adjusted net yards per attempt), but even this past season, the median pass attempt probably went for only one or two yards.
The average completion percentage was 61% while the sack rate was 5.9%; this means that on every 1,000 dropbacks, 59 times the QB was sacked. On the remaining pass plays, 574 times (61% of 941) of the time the QB completed a pass. So only 57.4% of all pass plays were completed, and surely a bunch of those completions went for negative yards or no gain.
In 1998, the completion percentage was 56.6% and the sack rate was 7.2%; this means only 4.8% of all completions would need to go for no gain (or worse) to make the median pass attempt be zero (or negative). In ‘88, the numbers were 54.3% and 6.8%; only 1.2% of completions would need to go for no gain (or worse) to make the median pass attempt be zero (or negative). In ‘78? A leaguewide completion percentage of 53.1% coupled with a sack rate of 7.9% meant that 51% of all pass plays did not gain yardage even ignoring all completed passes for negative or zero yards.
Passing is high risk, high reward. The large gains offset the risk, which is why teams average more yards per pass than yards per rush. For the passers, frequency of success isn’t nearly as important as quality of the success.
What about rushing? Just the opposite. In modern times, most RBs have a median carry length of three yards. I suspect that’s been the case for the majority of RBs for a long time. LenDale White and his 3.9 YPC last season? Median rush of 3 yards. Adrian Peterson and his 4.8 YPC? Median rush of 3 yards.