Proofing DeLong and Summers, "Fiscal Policy in a Depressed Economy":
Note that that required current-dollar 0.55 benefit-cost ratio includes as benefits:
- direct utility provided to current citizens,
- the present value of future GDP boosts from government capital,
- current aggregate-demand externalities, and
- the present value of future GDP boosts from reduced hysteresis effects on potential output.
At these interest rates, we surely are in the world of Abba Lerner's "functional finance"...