Ben Bernanke has cut interest rates a lot since last summer. But can he make a difference? Or is he just, as the old line has it, pushing on a string?

Here’s the Fed funds target rate (red line) — which is what the Fed actually controls — versus the interest rate on Baa corporate bonds (blue line), which is probably a better guide to what matters for actual business spending.

It’s pretty grim. Basically, deteriorating credit conditions have offset everything the Fed has done. Doubleplus ungood.