theorem variance_decay_nonneg (S₀ : ℝ) (hS : 0 ≤ S₀) (M : ℝ) (hM : 1 < M) (n : ℕ) :
0 ≤ S₀ * (1 - 1 / M) ^ n := by
apply mul_nonneg hS
apply pow_nonneg
have : 0 < 1 - 1 / M := by rw [sub_pos, div_lt_one (by linarith)]; linarith
linarithResults 86-92: Endogenous Variance Dynamics