theorem npvRevenue_zero_rate {B₀ η D₀ δ_gap : ℝ} : npvRevenue B₀ η D₀ δ_gap 0 = 0 := by simp only [npvRevenue, lafferRevenue, discountGap]; ring
thesis/CESProofs/Macro/GrowthTax.lean:207
Growth and Dynamic Tax Revenue (Layer 4-5 of Macro Extension)