The payroll tax cuts — just extended yesterday — are a bad idea for a number of reasons. In no particular order:

• They’ve provided zero measurable benefit to employment or economic growth.

• They add to our staggering deficit.

• They further compromise our already-bust entitlements system.

But there’s another reason. Turns out, the cuts are even more expensive than we thought. Here’s Kevin Williamson to explain:

The new deal on the payroll-tax extension (which will do little or nothing to benefit the economy) was held up by a largely unrelated matter: requiring federal workers to contribute more toward the costs of their own pensions. (More, Congress? How does 100 percent strike you?) The original proposal would have required all federal workers to bear more of the costs of their own retirements, but Democrats representing Maryland, that tony little suburb of Leviathan, shrieked. The compromise instead will cover only new hires.

We’ve gotten to the point where government can’t agree to give us back even just a little something-something, without first bribing itself. Pretty sure that means we’re deep into a positive-feedback loop, from which we’re unlikely to recover without first suffering a fiscal armageddon.