Four places where calibration disputes arise: (1) Shadow prices for institutional and natural capital are estimated, not observed — institutional capital is not yet integrated into any official wealth account. (2) Shadow prices are partly endogenous to the policy being evaluated. (3) The discount rate ρ involves an ethical choice (Stern vs Nordhaus spans roughly an order of magnitude on the social cost of carbon). (4) The internal/external boundary requires a convention for contested cases. But these are calibration disputes, not criterion disputes. Two honest analysts can disagree substantially on magnitudes while agreeing on the sign of ΔW_ext for most cases — and the sign is all the brake test requires.