Passing, rushing, and winning in the NFL since 1969

In January, after having a little fun with team stats for the 2009 NFL season, I looked at the correlations between success (wins) and per-play passing and per-play rushing throughout the early years of this century. The trend is clear--a strong passing game does a top-tier team make. Running is far less determinative.

But rule changes and a paradigmatic shift away from raw power to pure speed (the fullback, a linchpin position as recently as Daryl "Moose" Johnston of the nineties' Cowboys, is all but dead today) have increasingly led to the predominance of passing over running. This has not always been the case.

That has been my conception, anway. To see how well it meshes with reality, I ran the numbers extending all the way back to the 1969 season. The following table traces the last four decades, showing the correlations between winning and both passing yards per attempt and running yards per attempt by regular season:

Year	Pass	Run
2009	.80	.09*
2008	.48	.15*
2007	.76	.24*
2006	.44	.10*
2005	.60	.40
2004	.56	.45
2003	.67	.07*
2002	.50	.11*
2001	.39	.13*
2000	.47	.51
1999	.53	.12*
1998	.75	.32*
1997	.37	.27*
1996	.40	(.06)*
1995	.46	.28*
1994	.55	(.05)*
1993	.55	.34*
1992	.70	.08*
1991	.63	.33*
1990	.56	.05*
1989	.64	.04*
1988	.56	.16*
1987	.52	.15*
1986	.49	.03*
1985	.46	.13*
1984	.57	.09*
1983	.32	.42
1982	.51	.22*
1981	.21*	(.07)*
1980	.58	.19*
1979	.54	.11*
1978	.72	.09*
1977	.63	.30*
1976	.70	.29*
1975	.77	.34*
1974	.60	.16*
1973	.66	.47
1972	.50	.51
1971	.34*	.12*
1970	.57	.24*
1969	.48	(.24)*

* Not statistically significant at 95% confidence

The data dispute the preceding narrative. There is a lot of variation in the strength of the correlations from season to season, as is of course expected given that defense, special teams, penalties, schedules, etc are not taken into account. Still, passing has consistently been tied more tightly to success than running has been. In only three of the last 41 seasons has the relationship between rushing yards per attempt been more closely related to winning than passing yards per attempt has, and in each of those years--1972, 1983, 2000--running's advantage has been small.

The 2009 season, deemed the year only passing mattered, added an exclamation point to this observation. Over the last three decades, passing's importance has risen marginally, correlating with wins at .57 on average durings the 00s, from .52 in the eighties (.55 in the nineties)--but in the seventies, the average was .62. It's nothing new.

If, despite the reliably delivered claims coming from professional commentators during the playoffs to the contrary, passing matters most, why isn't the pass-to-run ratio more lopsided than it is?

Turnovers are one reason. In recent years, interceptions constitute about two-thirds of them, and some portion of the remaining one-third, coming in the form of fumbles, are lost by quarterbacks getting hit or receivers losing the ball after the catch. In 2009, a team's turnover balance (takeaways minus giveaways) correlated with games won at .69.

A one-dimensional approach putatively gives a big advantage to defenses as well--color commentators regularly describe running plays mid- and late-game as attempts by offenses to keep the opposing defenses "honest".

That said, I do wonder if, over time, there has been a shift toward more yards earned through the air relative to those on the ground. If passing's primacy is nothing new, maybe throwing the ball more is. Yet the diminution of the 1,000 yard rusher and the new benchmark of 2,000 yards in a single season suggests more, not less, yardage is being earned on the ground than before. I'll see what the history shows and present here.