[dragonwriter]

Indexing to revenue is a bit of a simplification. what I really think is the revenue stream should be split between current benefits and a reserve fund, with the reserve fund drawn from to avoid decreases in cyclical downturns. The idea is that the long-term effect should be increasing benefit with productivity, while avoiding short-term benefit drops.

And the effect you describe is really one of overall domestic spending, not one program in isolation.