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Mehdi Shadmehr

Publications and source records attributed to Mehdi Shadmehr.

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Designing Signals for Deterrence

States and alliances spend enormous resources signaling resolve to deter adversaries. Two canonical strategies are burning money (sunk costs) and burning bridges (audience costs). Large audience costs can deter effectively, but they may be infeasible and, even when feasible, can increase the likelihood of war relative to burning money. We propose a signaling design in which the defender retains the flexibility to fight or back down but commits ex ante, before learning its resolve, to a rule mapping realized resolve into costly actions. When audience costs are limited, this design raises defender payoffs while reducing the likelihood of war. We discuss implementation through laws and automated algorithms. We also characterize defender payoffs when audience costs are chosen endogenously from a feasible set, showing that lowering the maximum feasible audience cost can raise defender payoffs, and we compare these payoffs with those under the standard burning-money setting without commitment.

econ.TH

Algorithm Transparency and Search Manipulation: Steering vs. Persuasion

We study a platform that prefers to sell the more profitable of two products. It designs an algorithm that determines the product the consumer encounters first, conditional on her best match. The algorithm simultaneously manipulates consumer attention (steers) and communicates information about match quality (informs). When the algorithm is opaque, it is difficult for a consumer to understand how product order is generated and what it reveals. In the platform's preferred equilibrium, it places the profitable product first. When the algorithm is transparent, the consumer understands the algorithm and what it conveys. Thus, the algorithm can persuade as well as steer. In some cases, the equilibrium algorithm deters search, in others, encourages it. In the former case, transparency helps consumers; in the latter, it harms some or all of them. Extending or shifting transparency requirements uncouples steering from information provision, reverting the consumer's welfare to opacity.

econ.TH

Revealed and Concealed Repression: Theory and Measurement

Regimes routinely conceal acts of repression. We show that observed repression may be negatively correlated with total repression, consisting of both revealed and concealed acts. This distortion can generate perverse effects for policy interventions designed to reduce repression and complicates inference about the causes and consequences of repression. We develop a model in which regimes choose whether to conceal repression and activists decide whether to challenge the regime. We identify two measurement problems - one due to concealment and one to deterrence. We construct indices of repression that account for these problems and show how these indices can be expressed in terms of observable variables by leveraging equilibrium relationships. We then propose an empirical strategy to estimate these indices. As a proof of concept, we apply this approach to Russia, estimating repression indices at a monthly frequency for 2020-2025.

econ.TH

Signaling With Commitment

We study the canonical signaling game, endowing the sender with commitment power: before learning the state, sender designs a strategy, which maps the state into a probability distribution over actions. We provide a geometric characterization of the sender's attainable payoffs, described by the topological join of the graphs of the interim payoff functions associated with different sender actions. We then incorporate payoff irrelevant messages into the game, characterizing the attainable payoffs when sender commits to (i) both messages and actions, and (ii) only messages. By studying the tradeoffs between these model variations, we highlight the power of commitment to actions. We apply our results to the design of adjudication procedures and rating systems.

econ.TH