UPDATED: Did NFL Passer Ratings Spike in 2004 Or Have They Risen Steadily?

Update:  In order to simplify this article, I have updated it using gross passing numbers only per year.  Stats from 1940 to 2005 came from Cold Hard Football Facts, and are based on Gross numbers.  Please note that the numbers, run with gross or net passing yardage, yield the same results in terms of normal, predictable growth over time.

There is a common perception on BleacherReport and other sites, among writers and viewers alike, that the NFL went through a distinct and significant change in 2004—with a "spike" in league-wide QB passer ratings.

In fact, I've seen this argument used to claim that any QB stats post-2004 are somehow "over-inflated" because passing stats are easier to come by (i.e. it's much easier to be a QB now in the NFL than it used to be) because of this purported spike in passer rating. 

I decided to look into this further.  Everything I've seen has shown a steady progression in passer rating over the years.  There have been numerous spikes and depressions along the time line, but over time the ratings have "normalized" in a near linear upward progression. 

It's natural for all sports to evolve.  Players get bigger, stronger, faster.  Case in point, we see the 100m world record is broken every few years by some new sprinting phenom, as we did in the last Olympics with Usain Bolt.

Shouldn't we also expect QBs to evolve and become more efficient passers over time as they get bigger, stronger, and faster? Shouldn't they improve as better coaching and offensive schemes are developed?  Naturally we should expect this evolution.

Changes in the game have helped improve Passer Ratings as well.  Rule changes like the five yard contact rule for WRs have made significant impacts on the passing game.  Defenses haven't been consistent over the years either.  For instance, it is safe to say that in the modern NFL, the hardest time to be a Quarterback was 1966 to 1977, the Dead Ball Era.  13 of the 14 best defenses in modern NFL history played in this era.  Scoring was at a premium.  And Passer ratings submerged during this time period.  Being a QB today is easier than it has ever been with changes that have opened up the game on multiple fronts.

But to assume that "this" decade is the only decade that we've seen major changes is short sighted.  They've occurred repetitively through NFL history.

Suggesting a "spike" in league-wide passer rating in 2004 would indicate an "abnormal" jump in passer rating.  I will show how, instead, what we have seen is a normal progression in passer rating over time with no unusual spike.

In the appendix at the end of this article, I've provided the league-wide passer rating for all years in the NFL from 1940 to 2007 (omitting 2006 and 2008 for which I do not have the league-wide passer ratings calculated).

Did the League Wide Passer Rating "Jump" in 2004?

The short answer is yes, it increased in 2004.  The one year jump was a 4.5 increase in passer rating from the previous season.  In 2003, the league passer rating was 78.3.  In 2004 it jumped to 82.8, an increase of 4.5 in rating.  In a vacuum, single-year perspective, that certainly looks like a spike.

What is not being considered is that in 2002, two years prior, the league passer rating had risen to 80.4.  It dropped to 78.3 in 2003, making the uptick to 82.8 in 2004 look all the more drastic.  In fairness, the jump from 2002 to 2004 was only 2.4 points.

Also not considered is that in 2005 (the year after the spike), the league passer rating fell 2.7 points back down to 80.1, a passer rating lower than the 2002 mark of 80.4.  Here is a chronological list of league-wide passer ratings from 2000 to 2008:

• 2000—78.1
• 2001—78.5
• 2002—80.4
• 2003—78.3
• 2004—82.8
• 2005—80.1
• 2006—80.4
  
• 2007—82.6
• 2008 -83.2

Now, if you will, consider that the league-wide passer rating was 79.2 in 1995.  Yes, that's right, 79.2.  The difference in Passer Rating from 1995 to 2008 (14 seasons) has been 4.0 total passer rating points, or .29 points per season.

The increases, including the spikes and depressions, in passer rating this decade are actually rather low in the context of decade-by-decade comparisons (evidence to follow).

How Has Passer Rating Increased Over the Years?

Since 1940, the average increase per season in passer rating is .61 points per season. 

In 1940 the league passer rating was 42.3 and dropped in '41 to 39.6.  Since that time it has steadily (and with progression) increased over time to the 2008 level of 83.2. UPDATED: Click here to visually see the increase in passer rating since 1940: 

As you can see from the line graph, the league wide passer rating has shown upward progression in a near linear format since 1940.

Another way to look at the numbers is to look at the average passer rating per decade (taken as an average of the league wide passer rating for 10 seasons):

• 1940s—47.9
• 1950s—59.0
• 1960s—69.4
• 1970s—65.1
• 1980s—74.4
• 1990s—77.2
• 2000s—80.5

Apart from the '70s, that fell below the 60s (the Dead Ball Era), passer ratings have steadily increased since 1940.

If you look at those numbers further, you can see the following progression of increases in passer ratings by decade:

• 1950s—11.1 points higher than the 1940s average
• 1960s—10.4 points higher than the 1950s average
• 1970s—4.3 points lower than the 1960s average
• 1980s—9.3 points higher than the 1970s
• 1990s—2.8 points higher than the 1980s
• 2000s (to date)—3.3 points higher than the 1990s

In the present decade, passer ratings are only 3.3 points higher than those of the 90s, on average.  This decade's increase over the previous decade isn't even in the top 3 when compared to the 50s, 60s, and 80s jumps.  In fact, the increases in passer rating this decade are only (so far) .5 points higher than the 90s average. 

"Spike" Evidence

Since 1940, there have been notable single-year spikes and depressions in passer ratings.  The most notable single year increases in order are:

• 1946 to 1947:  9.6 jump
• 1942 to 1943:  8.3 jump
• 1961 to 1962:  7.8 jump
• 1953 to 1954:  7.5 jump
• 1978 to 1979:  5.8 jump
• 1944 to 1945:  5.2 jump

And the most notable single year drops are:

• 1969 to 1970: 7.8 drop
• 1976 to 1977: 6.3 drop
• 1943 to 1944: 6.2 drop
• 1948 to 1949: 6.1 drop
• 1965 to 1966: 6.1 drop
• 1954 to 1955: 4.5 drop

As you can see, nothing in the 2000 decade so far registers in the top 6 most notable historical spikes or the top 6 most notable drops.

Conclusion

In a vacuum, in 2004 we saw a jump in passer rating.  When taken in context, however, what we've seen in 2004 and this decade alone is a natural progression of the evolution of passer rating.  There was no spike so out of the ordinary that we should define 2004 as a "shifting point" in NFL quarterbacking and thus comparisons of QBs prior to 2004 and post 2004 are just as acceptable as comparing QBs from 2008 to say 2006. 

There is always a danger of comparing one QB from one generation to another, as there is in comparing QBs from one passing season to another.  The most effective way to use passer ratings to rate QB seasons is to compare a QB's passer rating with the league average of that same season.  In so doing, we see revealing numbers.  For instance, Peyton Manning's 2004 season, as remarkable as it was, ranked 26th in all NFL seasons for margin of performance greater than the league average (more on that later).  It was not nearly as spectacular, say, as Kenny Stabler's 1976 season where his 103.4 Passer Rating was 54.3% higher than the league average.

There is simply nothing that occurred in 2004 that prevents comparing a passer from say 2002 (80.4 league passer rating) to a post 2004 QB, or even 1995 (79.2) to 2002 (80.4).  Keep in mind, the difference between the league passer rating in 2008 and 2005 was a full 3.1 points.  Of course, it would be silly to look at the numbers this myopically.

Nothing is statistically out of the norm in terms of the increases in passer ratings over time.

Appendix:  League-Wide Passer Ratings from 1940 to 2008

Year    League Rating
1940    42.3
1941    39.6
1942    40.1
1943    48.4
1944    42.2
1945    47.4
1946    47.8
1947    57.6
1948    60
1949    53.9
1950    52.9
1951    55.6
1952    55.5
1953    54.2
1954    61.7
1955    57.2
1956    59.6
1957    63.2
1958    63.2
1959    66.9
1960    65.2
1961    64.8
1962    72.6
1963    71.7
1964    71.7
1965    73.5
1966    67.4
1967    66.6
1968    68.6
1969    71.6
1970    63.8
1971    62.2
1972    66.3
1973    64.9
1974    64.2
1975    65.6
1976    67
1977    60.7
1978    65
1979    70.8
1980    74.1
1981    72.9
1982    73.4
1983    75.9
1984    76.1
1985    73.6
1986    74.1
1987    75.2
1988    72.9
1989    75.6
1990    77.3
1991    76.2
1992    75.3
1993    76.6
1994    78.4
1995    79.2
1996    76.8
1997    77.2
1998    78.2
1999    77.1
2000    78.1
2001    78.5
2002    80.4
2003    78.3
2004    82.8
2005    80.1
2006    80.4
2007    82.6
2008    83.2