Still Thinking About Runners Left on Base

So I've kept thinking about Sterling and Waldman's inane rants about the Yankees inability to score runners from third with less than two outs, and I think I've figured out a way to measure the percentage of baserunners scored against the anticipated average.

Disclaimer: there are statistics here and some math, but nothing more complicated than algebra.  I never took pre-calc or calculus, and I got Cs and Bs (mostly Cs) in high school.  In college I took Music Theory instead of a math course.  Long story short- if I can do this math, so can you.  (I've cross posted this over at Beyond the Box Score  to see if I can get any of their brains to double check my work).

Everybody strapped in?

[(OBP+SLG)] * x = anticipated % of baserunners scored

I made the chart in Excel, and I've loaded a screenshot to Photobucket, but there's no way to get it onscreen clearly, so you'll have to go here to see it.

I started off charting % of baserunners scored against team slugging percentage, and I found a nearly direct relationship.  This makes perfect sense, right?  It takes 3 singles to score a run, 2 doubles, or one homer- so the higher the SLG, the higher the % of runners driven in.

So then the question that matters is: how good is the team at getting on base? 

By taking the average of %Scored for the last three seasons I solved for x, which is .503 in this sample.

We'd expect the Yankees to score 36.8% of their baserunners this season, compared to the 36.1% they've actually scored.  So I'd say they're performing exactly as we should expect.

Sterling and Waldman are right in comparison to the last couple of season, when the Yanks scored 41% and 42.2%.  Offense has been down across the entire league so far this season, and for the Yankees it's been an especially precipitous drop: .463 down to .423 on top of a OBP drop of .366 to .337.

The Yanks shouldn't expect to score much more until they improve their entire offense (duh, right?).