theorem cesMarkup_monopoly {σ : ℝ} (_hσ : 1 < σ) : cesMarkup 1 σ = σ / (σ - 1) := by simp only [cesMarkup, one_mul]
thesis/CESProofs/EntryExit/MarketStructure.lean:31
Paper 1, §22.5: Market Structure as CES Curvature