arXiv subjects

Masaki Miyashita

Publications and source records attributed to Masaki Miyashita.

6 recordsLinked to original sources

arXiv2026

On the Sparsity of Optimal Information Structures

This paper uncovers general properties of optimal information structures by exploiting a linear-programming formulation of information design. A critical observation is that an optimum can be found as ``sparse,'' i.e., many coordinates of the action-state joint distribution are zero. This implies that, once part of an action-state profile is fixed, there is limited room for the remaining part to fluctuate. As a result, agents' action recommendations are conditionally deterministic in many states, or correlated in a way that allows some agents to infer others' recommendations. The implications of sparsity are illustrated in an adoption problem, where the designer maximizes the number of adopters of an innovation that features network effects. The optimal information structure deterministically recommends full adoption in high states, while it randomizes over nested action profiles in low states, so that whenever an agent is recommended to adopt, she is certain that more optimistic agents also adopt.

econ.TH↗

arXiv2026

Identification of Information Structures in Bayesian Games

To what extent can an external observer infer the underlying information structure from an equilibrium action distribution in an incomplete-information game? We investigate this question in a general linear-quadratic-Gaussian framework. A simple class of canonical information structures is offered and proves rich enough to rationalize any equilibrium action distribution that can arise under an arbitrary information structure. Moreover, this class is parsimonious in the sense that its relevant parameters are uniquely identified from an observed equilibrium outcome. We then show that a canonical information structure characterizes the lower bound on the amount by which each agent's signal can reduce the state variance, across all observationally equivalent information structures. This identified lower bound can in turn be used to predict equilibrium action volatility following changes in the payoff structure.

econ.TH↗

arXiv2026

Characteristics Design: A Hedonic Approach to Optimal Product Differentiation

Building on the generalized hedonic-linear model of Pellegrino (2025), this paper studies optimal product differentiation when a representative consumer has preferences over product characteristics. Under multiproduct monopoly, the monopolist's choice of product characteristics is always aligned with the social planner's optimum, despite underproduction. By contrast, under oligopoly, multiple equilibria can arise that differ qualitatively in their patterns of characteristics design. We show that, while oligopoly equilibria exhibiting product differentiation yield higher welfare than those with product concentration, the degree of product differentiation under oligopoly remains below the socially optimal level. As a result, social welfare under oligopoly is typically lower than under monopoly, highlighting a key advantage of coordination in characteristics design. We extend the analysis to settings with overlapping ownership structures and show that common ownership can improve welfare by inducing firms to soften competition through increased product differentiation rather than output reduction.

econ.TH↗

arXiv2025

LQG Information Design

This paper addresses information design in a workhorse model of network games, where agents have linear best responses, the information designer maximizes a quadratic objective, and the payoff-relevant state follows a multivariate Gaussian distribution. We formulate the problem as a semidefinite program and establish strong duality to characterize the optimal information structure. A necessary and sufficient condition for optimality is given by a simple linear relationship between the induced equilibrium strategy profile and the state. Leveraging this characterization, we show that the state is fully revealed in an aggregative form for welfare maximization, while individual agents may remain only partially informed. When agent roles are interchangeable, the optimal information structure inherits the same degree of symmetry, which facilitates computation. In such cases, we show that the optimal amount of information revealed to each agent is closely linked to the network's chromatic number.

econ.TH↗

arXiv2024

On the Pettis Integral Approach to Large Population Games

The analysis of large population economies with incomplete information often entails the integration of a continuum of random variables. We showcase the usefulness of the integral notion à la Pettis (1938) to study such models. We present several results on Pettis integrals, including convenient sufficient conditions for Pettis integrability and Fubini-like exchangeability formulae, illustrated through a running example. Building on these foundations, we conduct a unified analysis of Bayesian games with arbitrarily many heterogeneous agents. We provide a sufficient condition on payoff structures, under which the equilibrium uniqueness is guaranteed across all signal structures. Our condition is parsimonious, as it turns out necessary when strategic interactions are undirected. We further identify the moment restrictions, imposed on the equilibrium action-state joint distribution, which have crucial implications for information designer's problem of persuading a population of strategically interacting agents. To attain these results, we introduce and develop novel mathematical tools, built on the theory of integral kernels and reproducing kernel Hilbert spaces in functional analysis.

econ.TH↗

arXiv2022

Twofold Multiprior Preferences and Failures of Contingent Reasoning

We propose a model of incomplete \textit{twofold multiprior preferences}, in which an act $f$ is ranked above an act $g$ only when $f$ provides higher utility in a worst-case scenario than what $g$ provides in a best-case scenario. The model explains failures of contingent reasoning, captured through a weakening of the state-by-state monotonicity (or dominance) axiom. Our model gives rise to rich comparative statics results, as well as extension exercises, and connections to choice theory. We present an application to second-price auctions.

econ.TH↗