Has Runs Created stopped working?
Does Runs Created not work any more?
The reason I ask is that, if you take a look at the 2008 AL and NL pages on Baseball Reference, you'll see that RC overestimated actual runs for 28 of the 30 teams. The average discrepancy was a huge +58 runs in the NL, and +19 runs in the NL.
To emphasize: that's not the average after removing the signs, that's the average *including* the signs. If half the teams had been +58 and the other half had been –58, the average would have been zero. It wasn't.
So what I'm saying is, Runs Created now appears to be biased too high.
This has been happening since the mid 90s. Here is the average team discrepancy by season:
Now, we know that Runs Created is biased too high for higher run environments, so that might be part of it. But it's not all of it. In the three seasons 1994 to 1996, there were 4.92, 4.84, and 5.03 runs per game respectively. But in 2005 there were only 4.59 runs per game, and in 2008, only 4.65 runs per game.
Could it be that the pattern of offensive events is different? Maybe there are different patterns of offensive events than there used to be (maybe more walks per single, or something?), and Runs Created doesn't work well when that happens?
By the way, I tried Base Runs, using the first version found on page 18 here (.pdf) with X=.535; the results weren't as extreme, but they were similar.
Anyone know what's going on? Is this a well-known problem and I just missed it?
P.S. For the record, I think I'm using the "technical" version of Runs Created found on this Wikipedia page.