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§3.2, p. 13 — high-type incentive condition iff θH/θL ≥ ΔH

Proved
CustomerVoice.ALearn.ich_iff_threshold

by mikedeng1 · Oct 15, 2026 · Mathlib 0df444a (Lean v4.33.1)

cheap-talkincentive-compatibilityp2o-batch-pfp2ap2o-gran-per-chapterp2o-plan-paperp2o-v1threshold

Under the A-Learning model's standing assumptions, the high-type buyer weakly prefers truthful communication to imitating the low type if and only if

θHθL≥ΔH=γ[2s+(1+γ)k](1−γ)(2s+γk).\frac{\theta_H}{\theta_L}\geq\Delta_H=\frac{\gamma[2s+(1+\gamma)k]}{(1-\gamma)(2s+\gamma k)}.θL​θH​​≥ΔH​=(1−γ)(2s+γk)γ[2s+(1+γ)k]​.

The buyer payoffs use the seller's design for the reported type and keep the nonpurchase option in both price-setting cases.

This gives the high-type component of the threshold in Proposition 1.

Formalization Note The weak inequality is the statement on p. 13 and in Proposition 1. The Appendix's corresponding strict-inequality line is read at equality using the weak incentive condition (6).

Preamble
import Mathlib
import Definitions.Def_CustomerVoice_ALearn_Setting
Formal statement
namespace CustomerVoice.ALearn

/-- §3.2, p. 13: the high-type IC condition is the threshold condition. -/
theorem ich_iff_threshold (M : Model) (hM : M.Standing) :
    M.ICH ↔ M.θH / M.θL ≥ M.DeltaH := by sorry

end CustomerVoice.ALearn
Source
Guo, The Voice of Customers in Customization, SSRN working paper 3994319 (version of 2023-11-29, https://ssrn.com/abstract=3994319), p. 13, §3.2, high-type threshold sentence following Proposition 1
Human review
  • Endorsed by Shuze Chen · Oct 16, 2026

    Confirmed by the moderator at approval.

  • Endorsed by mikedeng1 · Oct 16, 2026

    Confirmed by the mission captain (proposal self-audit).

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