theorem weakest_sector_crisis (e : NSectorEconomy N) (n : Fin N)
(hT : sectorCriticalFriction e n ≤ e.T n) :
sectorEffectiveCurvature e n = 0 := by
simp only [sectorEffectiveCurvature]
exact effectiveCurvatureKeff_above_critical _ _ _ _
(sectorCriticalFriction_pos e n) hTMultiplier-Cycle Duality in a Multi-Sector Economy