Over at TheGridFe, I just finished the single season portion of my series on the (statistically) greatest regular season quarterback performances in NFL history. I’ve discussed the stats, as they are, which always seem to paint modern quarterbacks in a much better light. I’ve prorated for season length, which can sometimes produce a few curious results. I’ve also applied both hard and soft inflation adjustments to account for the evolution of the position and increase in its usage rate. After talking with Adam Steele and agreeing that maybe even the most moderate approach still left seasons like Sid Luckman’s 1943 or Dan Fouts’s 1982 getting far more credit than they probably should. So I went ahead and made an even weaker era adjustment, which I will discuss briefly in this post, to try to mitigate the effects of the original modifications.

My main purpose for writing today isn’t to give you another list of great quarterback seasons, although I will do that as well. My goal is to solicit the opinions of the Football Perspective readers, whom I respect for their thoughtful and reasoned nature. I have two primary questions:

Is it necessary, or even right, to make adjustments for changes in both schedule and QB usage rates? If we believe it is right to reward older players with schedule and inflation corrections, should we also penalize them for playing in weaker leagues?

I will provide two tables below with several examples of what it looks like to make the changes I mentioned in the first question. I have no such table for the second question. In fact, this study from Jason Lisk is the only attempt I have seen at comprehensive comparison of the relative strengths of the NFL and AFL. I’ll talk a little about both after we look at some numbers.

The Basics

Since the NFL began running a standardized schedule (1936), there have been 94 professional seasons between the established league and its two greatest rivals. In those years, we have seen schedules range from a mere nine games to the current sixteen-game format. We have also seen a range of quarterback plays per game from 19.5 to 40.9. As you’ll see, this can create pretty extreme numbers when we attempt to put these seasons on a level playing field.

The table below probably isn’t for everyone, but I think many among you will find it instructive. It displays the 94 seasons mentioned above, along with the numbers we get after using different methods to prorate and adjust for inflation. Read it thus: The 2015 NFL featured a 16-game schedule and saw quarterbacks engage in 40.8 plays per game. The multiplier to prorate the schedule is 1.00 (16/16). To find the lower multiplier, just take the average of the higher multiplier and 1.00. In this case, the lower multiplier is still 1.00. To find the hard inflation adjustment, take the season’s plays per game and divide it into the historical plays per game (34.7). For 2015, that number is 0.85. To arrive at the soft inflation adjustment, find the average of the hard adjustment and 1.00. For 2015, that’s 0.93. To find the weakest adjustment, divide the sum of the hard adjustment and two by three [(0.85 + 2)/3]. The quotient is 0.95 for 2015. Once you have those figured out, you can used any combination of schedule and inflation adjustment to modify a quarterback’s yearly value. The last six columns show us what we end up doing to a season once we apply these combinations.

Year LG P/G Pro Low Hard Soft Weak ProHard ProSoft ProWeak LowHard LowSoft LowWeak NFL2015 16 40.8 1 1 0.85 0.93 0.95 0.85 0.93 0.95 0.85 0.93 0.95 NFL2014 16 40.9 1 1 0.85 0.92 0.95 0.85 0.92 0.95 0.85 0.92 0.95 NFL2013 16 40.6 1 1 0.86 0.93 0.95 0.86 0.93 0.95 0.86 0.93 0.95 NFL2012 16 40.2 1 1 0.86 0.93 0.95 0.86 0.93 0.95 0.86 0.93 0.95 NFL2011 16 39.3 1 1 0.88 0.94 0.96 0.88 0.94 0.96 0.88 0.94 0.96 NFL2010 16 38.6 1 1 0.9 0.95 0.97 0.9 0.95 0.97 0.9 0.95 0.97 NFL2009 16 37.8 1 1 0.92 0.96 0.97 0.92 0.96 0.97 0.92 0.96 0.97 NFL2008 16 37.6 1 1 0.92 0.96 0.98 0.92 0.96 0.98 0.92 0.96 0.98 NFL2007 16 37.3 1 1 0.93 0.97 0.98 0.93 0.97 0.98 0.93 0.97 0.98 NFL2006 16 37.4 1 1 0.93 0.97 0.98 0.93 0.97 0.98 0.93 0.97 0.98 NFL2005 16 37 1 1 0.94 0.97 0.98 0.94 0.97 0.98 0.94 0.97 0.98 NFL2004 16 37 1 1 0.94 0.97 0.98 0.94 0.97 0.98 0.94 0.97 0.98 NFL2003 16 37.7 1 1 0.92 0.96 0.97 0.92 0.96 0.97 0.92 0.96 0.97 NFL2002 16 38.1 1 1 0.91 0.96 0.97 0.91 0.96 0.97 0.91 0.96 0.97 NFL2001 16 38.8 1 1 0.9 0.95 0.97 0.9 0.95 0.97 0.9 0.95 0.97 NFL2000 16 38.8 1 1 0.89 0.95 0.97 0.89 0.95 0.97 0.89 0.95 0.97 NFL1999 16 38.6 1 1 0.9 0.95 0.97 0.9 0.95 0.97 0.9 0.95 0.97 NFL1998 16 38.4 1 1 0.9 0.95 0.97 0.9 0.95 0.97 0.9 0.95 0.97 NFL1997 16 38.1 1 1 0.91 0.96 0.97 0.91 0.96 0.97 0.91 0.96 0.97 NFL1996 16 38.7 1 1 0.9 0.95 0.97 0.9 0.95 0.97 0.9 0.95 0.97 NFL1995 16 38.7 1 1 0.9 0.95 0.97 0.9 0.95 0.97 0.9 0.95 0.97 NFL1994 16 38.4 1 1 0.91 0.95 0.97 0.91 0.95 0.97 0.91 0.95 0.97 NFL1993 16 36.9 1 1 0.94 0.97 0.98 0.94 0.97 0.98 0.94 0.97 0.98 NFL1992 16 36 1 1 0.96 0.98 0.99 0.96 0.98 0.99 0.96 0.98 0.99 NFL1991 16 35.4 1 1 0.98 0.99 0.99 0.98 0.99 0.99 0.98 0.99 0.99 NFL1990 16 36 1 1 0.96 0.98 0.99 0.96 0.98 0.99 0.96 0.98 0.99 NFL1989 16 36.3 1 1 0.96 0.98 0.99 0.96 0.98 0.99 0.96 0.98 0.99 NFL1988 16 37 1 1 0.94 0.97 0.98 0.94 0.97 0.98 0.94 0.97 0.98 NFL1987 15 37.2 1.07 1.03 0.93 0.97 0.98 1 1.03 1.04 0.97 1 1.01 NFL1986 16 37.5 1 1 0.93 0.96 0.98 0.93 0.96 0.98 0.93 0.96 0.98 NFL1985 16 37.4 1 1 0.93 0.96 0.98 0.93 0.96 0.98 0.93 0.96 0.98 NFL1984 16 37 1 1 0.94 0.97 0.98 0.94 0.97 0.98 0.94 0.97 0.98 NFL1983 16 36.6 1 1 0.95 0.97 0.98 0.95 0.97 0.98 0.95 0.97 0.98 NFL1982 9 36.1 1.78 1.39 0.96 0.98 0.99 1.71 1.74 1.76 1.34 1.36 1.37 NFL1981 16 35.7 1 1 0.97 0.99 0.99 0.97 0.99 0.99 0.97 0.99 0.99 NFL1980 16 34.8 1 1 1 1 1 1 1 1 1 1 1 NFL1979 16 33 1 1 1.05 1.03 1.02 1.05 1.03 1.02 1.05 1.03 1.02 NFL1978 16 31.2 1 1 1.11 1.06 1.04 1.11 1.06 1.04 1.11 1.06 1.04 NFL1977 14 30.4 1.14 1.07 1.14 1.07 1.05 1.31 1.23 1.2 1.23 1.15 1.12 NFL1976 14 30.7 1.14 1.07 1.13 1.07 1.04 1.29 1.22 1.19 1.21 1.14 1.12 NFL1975 14 31.2 1.14 1.07 1.11 1.06 1.04 1.27 1.21 1.19 1.19 1.13 1.11 NFL1974 14 30.5 1.14 1.07 1.14 1.07 1.05 1.3 1.22 1.2 1.22 1.15 1.12 NFL1973 14 29.6 1.14 1.07 1.17 1.09 1.06 1.34 1.24 1.21 1.26 1.16 1.13 NFL1972 14 29.1 1.14 1.07 1.19 1.1 1.06 1.36 1.25 1.22 1.28 1.17 1.14 NFL1971 14 29.8 1.14 1.07 1.17 1.08 1.06 1.33 1.24 1.21 1.25 1.16 1.13 NFL1970 14 30.7 1.14 1.07 1.13 1.07 1.04 1.29 1.22 1.19 1.21 1.14 1.12 NFL1969 14 31.4 1.14 1.07 1.11 1.05 1.04 1.26 1.2 1.18 1.19 1.13 1.11 NFL1968 14 32.2 1.14 1.07 1.08 1.04 1.03 1.23 1.19 1.17 1.16 1.11 1.1 NFL1967 14 32.8 1.14 1.07 1.06 1.03 1.02 1.21 1.18 1.17 1.14 1.1 1.09 NFL1966 14 33.3 1.14 1.07 1.04 1.02 1.01 1.19 1.17 1.16 1.12 1.09 1.09 NFL1965 14 33.5 1.14 1.07 1.04 1.02 1.01 1.19 1.17 1.16 1.11 1.09 1.09 NFL1964 14 32.9 1.14 1.07 1.06 1.03 1.02 1.21 1.18 1.16 1.13 1.1 1.09 NFL1963 14 32.9 1.14 1.07 1.05 1.03 1.02 1.21 1.17 1.16 1.13 1.1 1.09 NFL1962 14 29.3 1.14 1.07 1.19 1.09 1.06 1.36 1.25 1.21 1.27 1.17 1.14 NFL1961 14 29 1.14 1.07 1.2 1.1 1.07 1.37 1.26 1.22 1.28 1.18 1.14 NFL1960 12 28.8 1.33 1.17 1.21 1.1 1.07 1.61 1.47 1.42 1.41 1.29 1.25 NFL1959 12 28.8 1.33 1.17 1.21 1.1 1.07 1.61 1.47 1.43 1.41 1.29 1.25 NFL1958 12 28 1.33 1.17 1.24 1.12 1.08 1.65 1.49 1.44 1.45 1.31 1.26 NFL1957 12 27.2 1.33 1.17 1.28 1.14 1.09 1.7 1.52 1.46 1.49 1.33 1.27 NFL1956 12 27 1.33 1.17 1.29 1.14 1.1 1.72 1.52 1.46 1.5 1.33 1.28 NFL1955 12 28.7 1.33 1.17 1.21 1.1 1.07 1.61 1.47 1.43 1.41 1.29 1.25 NFL1954 12 30.9 1.33 1.17 1.12 1.06 1.04 1.5 1.42 1.39 1.31 1.24 1.22 NFL1953 12 31 1.33 1.17 1.12 1.06 1.04 1.49 1.41 1.39 1.31 1.24 1.21 NFL1952 12 30.8 1.33 1.17 1.13 1.06 1.04 1.51 1.42 1.39 1.32 1.24 1.22 NFL1951 12 30.4 1.33 1.17 1.14 1.07 1.05 1.52 1.43 1.4 1.33 1.25 1.22 NFL1950 12 30.6 1.33 1.17 1.14 1.07 1.05 1.51 1.42 1.39 1.32 1.25 1.22 NFL1949 12 29.8 1.33 1.17 1.17 1.08 1.06 1.55 1.44 1.41 1.36 1.26 1.23 NFL1948 12 28.7 1.33 1.17 1.21 1.11 1.07 1.62 1.47 1.43 1.41 1.29 1.25 NFL1947 12 28.3 1.33 1.17 1.23 1.11 1.08 1.64 1.49 1.44 1.43 1.3 1.26 NFL1946 11 27.7 1.45 1.23 1.26 1.13 1.09 1.83 1.64 1.58 1.54 1.38 1.33 NFL1945 10 27.8 1.6 1.3 1.25 1.12 1.08 2 1.8 1.73 1.62 1.46 1.41 NFL1944 10 24 1.6 1.3 1.45 1.22 1.15 2.31 1.96 1.84 1.88 1.59 1.49 NFL1943 10 25.3 1.6 1.3 1.37 1.19 1.12 2.19 1.9 1.8 1.78 1.54 1.46 NFL1942 11 27 1.45 1.23 1.28 1.14 1.1 1.87 1.66 1.59 1.58 1.4 1.34 NFL1941 11 27.6 1.45 1.23 1.26 1.13 1.09 1.83 1.64 1.58 1.54 1.39 1.33 NFL1940 11 28.3 1.45 1.23 1.23 1.11 1.08 1.78 1.62 1.56 1.51 1.37 1.32 NFL1939 11 27.7 1.45 1.23 1.25 1.13 1.08 1.82 1.64 1.58 1.54 1.38 1.33 NFL1938 11 25.3 1.45 1.23 1.37 1.19 1.12 1.99 1.72 1.63 1.68 1.46 1.38 NFL1937 11 21.7 1.45 1.23 1.6 1.3 1.2 2.33 1.89 1.75 1.96 1.6 1.47 NFL1936 12 19.5 1.33 1.17 1.78 1.39 1.26 2.38 1.86 1.68 2.08 1.62 1.47 AFL1969 14 33 1.14 1.07 1.05 1.03 1.02 1.2 1.17 1.16 1.13 1.1 1.09 AFL1968 14 33.7 1.14 1.07 1.03 1.02 1.01 1.18 1.16 1.16 1.11 1.09 1.08 AFL1967 14 34 1.14 1.07 1.02 1.01 1.01 1.17 1.16 1.15 1.09 1.08 1.08 AFL1966 14 34.4 1.14 1.07 1.01 1.01 1 1.16 1.15 1.15 1.08 1.08 1.08 AFL1965 14 35 1.14 1.07 0.99 1 1 1.13 1.14 1.14 1.06 1.07 1.07 AFL1964 14 34.6 1.14 1.07 1 1 1 1.15 1.15 1.14 1.08 1.07 1.07 AFL1963 14 34 1.14 1.07 1.02 1.01 1.01 1.17 1.16 1.15 1.1 1.08 1.08 AFL1962 14 33.4 1.14 1.07 1.04 1.02 1.01 1.19 1.17 1.16 1.11 1.09 1.09 AFL1961 14 34.2 1.14 1.07 1.02 1.01 1.01 1.16 1.15 1.15 1.09 1.08 1.08 AFL1960 14 34.7 1.14 1.07 1 1 1 1.14 1.14 1.14 1.07 1.07 1.07 AAFC1949 12 28.2 1.33 1.17 1.23 1.12 1.08 1.64 1.49 1.44 1.44 1.3 1.26 AAFC1948 14 27.3 1.14 1.07 1.27 1.14 1.09 1.45 1.3 1.25 1.36 1.22 1.17 AAFC1947 14 26.6 1.14 1.07 1.31 1.15 1.1 1.49 1.32 1.26 1.4 1.24 1.18 AAFC1946 14 25 1.14 1.07 1.39 1.2 1.13 1.59 1.37 1.29 1.49 1.28 1.21

Depending on which combination of adjustments you implement, your results can vary drastically. The last few seasons receive the most significant possible penalties, with their values only given 85% credit in some cases. On the other hand, quarterbacks in 1936 receive as much as 238% credit for their output. I know this isn’t important to some of you, and it might not even be that helpful in the abstract, but I think it’s a useful tool to see how much credit we are adding – or taking away from – players based on the era they happened to play football. If you’re more interested in a practical example of what this means, you may prefer the next table.

The Results

To set up the table below, I calculated every quarterbacks Total Adjusted Yards per Play since 1932. I then found their efficiency relative to the rest of the league. This is similar to how Chase calculates RANY/A, but for a few small differences: first, I back out the player’s stats from the rest; second, I aggregate years n – 1, n, and n + 1 prior to finding the average. The result is what I have called value per play. All we have to do now is multiply Val/P by total plays to find total value over average.

Once we have the actual, unadulterated value, we can apply our combinations of era modifiers to see what happens. I have done just that. Read thus: Peyton Manning, playing in the 2004 NFL, had 535 plays at a rate of 9.16 TAY/P. His marginal value of 4.32 leads to a total value over average of 2312, tops in history. However, that value changes to 2171 with a ProHard modification, 2241 with a ProSoft modification, and 2265 with a ProWeak modification. Because he played in a 16-game season, his LowHard, LowSoft, and LowWeak modifications are the same as his Pro ones.

The most glaring issue that arises is what happens when we sort by the ProHard column. Not only does Luckman’s 1943 season jump to the top, it does so by an astronomical margin. Some might argue that he was a dominant force that year and deserving of the top spot. I think 1943’s 2.19 total multiplier gives him way too much credit. I’d say the same for Fouts in 1982, as well as for every quarterback to play in a 12-game-or-less season. It isn’t until I apply the weakest of all era adjustments that Manning and Dan Marino jump back to the top two spots. Luckman still outranks Tom Brady’s blitzkrieg 2007 campaign. It’s clear to me that seasons with low attempts, whether because of a shorter schedule or lower usage rate of passers, seem to receive undue credit. Perhaps that’s a nice balance to the fact that those seasons rarely receive proper credit from fans in real life. I don’t know.

Maybe the issue isn’t that I am adjusting for era so harshly. Maybe the real issue is that I am doing so without discounting for the relative weakness of the league that Luckman (or Sammy Baugh, or Cecil Isbell, or Otto Graham, or George Blanda) dominated. That’s where the second question I asked at the beginning comes in. Is it a good idea to start applying some sort of discount to these eras? If we do, should it be based on rigorous analysis, or should it be based on what feels right? I don’t have the answers to these questions. If I did, I wouldn’t crave your input. What do you, esteemed readers of Football Perspective, think about the idea of era adjustments and discounts?

Let me know in the comments. Thanks for reading.