40 and Fabulous: in praise of passer rating

Cold, Hard Football Facts for Jun 11, 2012



By Kerry J. Byrne
Cold, Hard Football Facts Professor of Footballogy


The Cold, Hard Football Facts were invited to NFL Films this past weekend to speak about statistical analysis at the Pro Football Researchers Association bi-annual meeting.

Needless to say, we packed up the PIGSKIN F-150 world-class tailgate machine and hit the road down to NFL Films headquarters in Mt. Laurel, New Jersey, just a few miles east of Philadelphia.
 
CHFF contributor Ken Crippen is the executive director of the PFRA and pieced together a great panel of topics.

Our presentation was called "40 and Fabulous: In Praise of Passer Rating." We explained why there is much more to passer rating than just a way to measure quarterback efficiency. We explained why this indicator, which celebrates 40 years as an official stat this season, is actually the Mother of All Stats. The entire powerpoint presentation can be seen below.
 
Sal Paolantonio of ESPN gave the keynote address. It turns out he is more than just the poor guy who must suffer through Merril Hoge’s endless rants about “establishing the run” on the NFL Matchup show.
 
Paolantonio discussed his recent book, “How Football Explains America.” The CHFFs have not yet read the book, but certainly will, especially after hearing Paolantonio talk about its origins. In fact, it’s the book we always wanted to write and quite jealous he beat us to the punch.
 
Paolantonio is a former Navy officer and a student of history. He dives into American cultural, military and sporting history – all the things we love – to describe why a unique nation is so passionate about a unique sport. Paolantonio said he was inspired by the book, “How Soccer Explains the World.”
 
“I heard about that book and thought to myself, ‘Wait a minute. Soccer doesn’t explain the U.S.,” said Paolantonio. Sounds like a great read. We’re picking it up this week.
 
We gave the first address to the PFRA members Saturday morning. We used the opportunity not to simply tout the great Quality Stats that we invented, but to give a little love to and provide some unique ways to look at passer rating. Specifically, we discussed our unique ways of using the passer rating formula to explain so much about NFL history and smash so many tired old myths in the process.
 
Passer rating was adopted by the NFL in 1973. That means the 2012 season will be its 40th year as an “official” NFL stat. People bitch about passer rating all the time. But, quite frankly, it doesn’t get enough love. We’ve discovered that few stats in sports are better at separating winners from losers.
 
In fact, the guys who invented it, probably don’t know how good it is. Football analysts disrespect it all the time. But the PFRA members seemed impressed by our analysis – because we brought a heavy hammer of Cold, Hard Football Facts to support our argument.
 
Here’s a look at the powerpoint we put together to guide the conversation, as well as some very quick notes that we discussed about each slide. Much of this will be familiar to long-time CHFF loyalists (Hi Cousin Cooter!). But there’s some new info in here, too, including the five-year “correlation to victory” records of various key indicators.



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The folks who created the passer rating formula (Don Smith, Seymour Siwoff and Don Weiss) did it merely as a way to measure the quality of each passer with something better than mere passing yards. As CHFF readers know, passing yards in and of themselves are useless without any statistical context. And passing yards had a very low correlation to victory.

So the guys who created passer rating were heading in the right direction. However, we doubt they realized back then just how awesome passer rating really is, when applied appropriately to analysis of pro football on BOTH sides of the ball.


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Passer rating is certainly a rock-solid way to measure the effectiveness of a quarterback or a team's passing attack in general. However, the indicator's capabilities are not fully realized until you do what we do with passer rating here at CHFF: apply the formula to team pass defense (Defensive Passer Rating) and then to overall team effectiveness on both sides of the ball (Passer Rating Differential). PRD is so good that we call it the Mother of All Stats.

Passer ratings most vocal critics typically attack the methodology behind it. We understand the methodology opens the door to plenty of questions. So you can argue with the methodology. But you can't argue with the results. Passer rating is a highly effective way to measure so much more than passing success. It's an incredible way to measure team success, too ... poor methodology or not.
 
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NFL insiders, even Super Bowl-winning coaches, often attack passer rating. It's shocking that even folks at the top of the game are so oblivious to the awesome power of this indicator. Brian Billick, coach of the 2000 Super Bowl champion Ravens, is wrong about passer rating on two counts. One, he calls it quarterback rating. it is NOT a quarterback rating. It merely measures how effectively a quarterback (or a team) passes the football. It purports to measure nothing else but passing.

Two, he should be the last person in the world to criticize passer rating. In fact, his 2000 Ravens won the Super Bowl solely on the back of its dominance of the passing game, as proven by Passer Rating Differential. We addressed Billick's misunderstanding about the statistical foundation of his own success after he made these comment two years ago.
 
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CHFF's "Correlation to Victory" is not true correlation in the actual mathematical and scientific definition of the word. We use the phrase to demonstrate how often teams win games when they win particular statistical battles.

Teams that won the passer rating battle (i.e., teams that won the battle of Passer Rating Differential) have won about 80 percent of all NFL games in the five years since the 2007 season. That number is fairly consistent throughout all of NFL history, too. Most importantly, the top four indicators on this list are all measures of passing efficiency. Rusing indicators, such as rushing yards and rushing YPA, are well down the list.

Great teams sometimes run very well and very far; sometimes they suck running the ball. The one consistent theme among all great teams in history is that they all won because they won the battles of passing efficiency. No team in history won a title purely but outmuscling teams on the ground. But plenty of poor running teams have won titles thanks to dominance of the skies over NFL battlefields.

Total passing yards well down the list, too. As we noted during the presentation, and many times here on CHFF, the last QB to lead the NFL in passing yards and win a championship was Johnny Unitas in 1959. That's more than a half century ago, for those of you keeping score at home. 

 
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The Correlation to Victory of Passer Rating Differential is extremely consistent. It has ranged from .785 to .805 over the past five seasons, a narrow difference of just 2/100th of a point.

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There is a pervasive and erroneous belief among NFL fans and analysts that the passing game has grown more important in recent years. The passing game has NOT grown more important in recent years. It's simply grown more common, as teams pass more. But the reality is dominance on the field has always been the direct result of dominance in the passing game, at least since the dawn of the T-formation era in the NFL in 1940.

The beauty of Passer Rating Differential is that it works across all eras. Sure, passer ratings in general are much higher now than they were in years past. So it's certainly not fair to equate a passer rating of 90 today (yawn) with a passer rating of 90 in the 1940s (wow!). You'd have to normalize across eras to make that equation a fair comparison. But within the context of each era, one thing is always true: games and seasons are always dominated by teams that dominate the battle of Passer Rating Differential.
 
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(* denote NFL champions). The Chicago Bears adopted in 1940 the T-formation that had been pioneered in the college game. The most famous example of the power of the new offensive formation is found in the 1940 NFL championship game: the Bears beat the Redskins, 73-0. It's still the biggest blowout in NFL history.

But that game is a little misleading, at least when it comes to demonstrating the power of the T-formation. The Bears passed the ball just 10 times that day, with one passing TD. The Redskins attempted a ridiculous-for-the-era 51 passes. Eight of those passes were picked off and three were returned for touchdowns. The game was a demonstration of the power of Passer Rating Differential. Chicago won the PRD battle by an unbelieavable margin of 145.8 to 13.6 (+132.2).

But the Bears had yet to fully exploit the T-formation on offense in that game.

Instead, if you're looking for the statistical manifestation of Chicago's dominance with the new T-formation, which emphasized the quarterback as a passer, you'll find it here on the list of the most dominant teams in history in Passer Rating Differential. The Bears of early 40s hold the three top spots on the list with simply ridiculous numbers.

Put another way, the Chicago Bears of the early 1940s were playing offensive chess while everybody else was still playing checkers, struggling to adopt or refusing to adopt the T-formation. The Bears of 1941-43 went 29-2-1 and won two NFL championships. This era also included the single most dominant team in the history of the NFL. The 1942 Bears went 11-0, scored 376 points and surrendered just 84 points. Of course, that dominant team, like the dominant undefeated 2007 Patriots, was upset in the NFL championship game. 
 
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(* denote NFL champions). We modernize the all-time best in Passer Rating Differential a bit by bringing it up to only the Super Bowl Era. Vince Lombardi's Super Bowl I champion 1966 Packers were the best of the past 46 years in Passer Rating Differential ... interesting because his Packers are remembered for a great ground game. But more on :Lombardi's Packers in a moment.

Five of these 10 teams won the Super Bowl and all but one of them were very good. The historic sad-sack Lions can never catchh a break. And the 1976 Lions were no exception: despite being one of the 10 best of the Super Bowl Era dominating the passing lanes, they couldn't even win half their games.

Every rule has its exception, and the 1976 Lions are certain an exception to the rule about Passer Rating Differential. It's something of a statistical miracle then went only 6-8 despite a +40.9 mark in PRD. Without even looking, we can tell you that this team was VERY bad in situational football and probably ranked very low on Scoreability and Bendability, our measures of offensive and defensive efficiency.

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(* denote NFL champions). Finally, we bring the Top 10 in PRD up to the Live Ball Era, the period since the rule changes of 1978 that opened up the passing game. The differentials are not as high in modern times as they have been in the past.

One reason is that we do have some semblance of statistical "parity" in the modern NFL. It's harder for one team or a handful of teams to dominate talent or strategy like they might have in past years when the league was a lot less stable and teams came and went. Another reason is that it's just so damn hard to play pass defense these days. It's VERY rare in the modern NFL to see Defensive Passer Ratings in the 40s or even the 50s. It was quite common to see those low DPRs right through the 1970s.

The list of the top 10 in PRD on the Live Ball Era includes six champions, one 16-0 team, one 15-1 team and Bill Walsh's 13-2 team of 1987. Those 1987 49ers are a bit of an anomaly: 1987 was a strike season and teams played three games that year with replacement players.

By the way, look at those 1988 Minnesota Vikings. They're the worst team on the list at 11-5, but boasted the best pass defense of the Live Ball Era. They picked off 36 passes that season, a ridiculous number you might have only seen before in the wild, INT-prone early days of the AFL and its inferior quarterbacks.
 
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Our discovery a few years ago that Vince Lombardi's 1960s Packers consistently dominated through the air was the finding that made us true believers in the power of Passer Rating Differential.

The romanticized image is that Lombardi's Packers won the "old-fashioned" way by dominating opponents with its smash-mouth ground game. The 1962 team certainly won that way. In fact, it may have been the best rushing team in the history of football. And that team etched in historic stone the image of Lombardi's three-yards-and-a-cloud-of-dust Packers that is still so powerful today.

The statistical reality is quite a bit different than the image, however. Lombardi's Packers varied wildly in their ability to run the ball. Some years, like 1962, they were great. Other years, like 1966, they were awful.

But there was one constant: Lombardi's Packers consistently dominated the passing lanes. Lombardi's Packers, in other words, won through the air, not on the ground.

The Super Bowl II champion 1967 Packers, by the way, finished No. 3 in PRD that season, Lombardi's only champs who did not rank No. 1 in PRD. But they were utterly domiant in the famous postseason run over the Rams, Cowboys (in the Ice Bowl) and Raiders (in Super Bowl II). The struggling 9-4-1 Packers of 1967 recaptured the old magic in the playoffs, with a remarkable +42.8 Passer Rating Differential in those three games.

One listener at NFL Films Saturday cried "heresy!" upon hearing this data. But admitted his astonishment: "How come I never heard any of this before?" he asked.

Well, that's why the Cold, Hard Football Facts are here, folks, to set the record straight and wipe out the misinformation that clouds so much about NFL history and analysis. We wrote about Lombardi's pass-dominant Packers many times here on CHFF as well as on SI.com.
 
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Bill Walsh's 49ers provide similar evidence of the power of Passer Rating Differential. Everybody knows Walsh's 49ers, and the system he put in place, consistently produced brutally efficient numbers in the passing game, including record efficiency in the passing game.

But that innovative West Coast offense is not why Walsh is a genius or why the 49ers won so consistently over nearly two decades. Nope. Walsh's genius and the reason why the 49ers won so consistently over nearly two decades is that Walsh paired the West Coast offense with one of the great pass-defense dynasties in the history of football. That dynasty began the day that future Hall of Famer Ronnie Lott stepped on the field as a rookie in 1981.

He wrote about this phenomenon in great detail righ there.
 
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Eight teams utterly dominated the NFL on both sides of the ball: No. 1 in Offensive Passer Rating and No. 1 in Defensive Passer Rating. Naturally, these teams were also No. 1 in Passer Rating Differential.

The most interesting team on the list is the Colts of the late 1950s. Johnny Unitas is obviously one of the great quarterbacks in history. And his performances, as measured by his raw numbers and the analysis of the Cold, Hard Football Facts, look even more impressive with each passing season. He put up numbers that leaped off the stat sheet in his era and many of them still stand the test of time today.

But he also had the luxury of playing two years in a row with the NFL's best pass defense. The Colts won championships in both 1958 and 1959 and were No. 1 across the board in OPR, DPR and PRD both seasons. No team in history had evern pulled off that feat two years in a row.

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