Andrew Ellis
Assistant Professor of Economics
Contact
Department of Economics
London School of Economics
Houghton Street
London
WC2A 2AE
Email: a[dot]ellis[at]lse.ac.uk
UK Phone: +44(0)2079556868
US Phone: +1(919)8898298
Curriculum Vitae (pdf)
Research Interests
Microeconomic Theory
Decision Theory
Publications
 On Dynamic Consistency in Ambiguous Games (2018). Games and Economic Behavior, accepted.
Abstract.
I consider static, incomplete information games where players may not be ambiguity neutral. Every player is one of a finite set of types, and each knows her own type but not that of the other players. Exante, players differ only in their taste for outcomes. If every player is dynamically consistent with respect to her own information structure, respects consequentialism, and has at least two possible types, then the function representing beliefs must be additive on types.

Foundations for Optimal Inattention (2018). Journal of Economic Theory, 173:5694.
Abstract.
This paper models an agent who has a limited capacity to pay attention to information and thus conditions her actions on a coarsening of the available information. The main result provides properties of the agent's conditional choices that are necessary and sufficient for the following as if interpretation: she chooses both her coarsening and her actions by constrained maximization of an underlying subjective expected utility preference relation. Observing these choices permits unique identification of the agent's utility index, cognitive constraint and prior (the last under a suitable richness condition). An application considers a market in which strategic firms offer differentiated products. If the consumer's information concerns firms' quality, then equilibrium consumer surplus may be higher with an optimally inattentive consumer than with one who processes all available information.
Supplementary material.

Correlation Misperception in Choice, with M. Piccione (2017). American Economic Review, 107(4):126492.
Abstract.
We present a decisiontheoretic analysis of an agent's understanding of the
interdependencies in her choices. We provide the foundations for a simple and
flexible model that allows the misperception of correlated risks. We introduce
a framework in which the decision maker chooses a portfolio of assets among
which she may misperceive the joint returns, and present simple axioms
equivalent to a representation in which she attaches a probability to each
possible joint distribution over returns and then maximizes subjective
expected utility using her (possibly misspecified) beliefs.
An earlier version, "Complexity, Correlation, and Choice", with more results.

Condorcet Meets Ellsberg (2016). Theoretical Economics, 11(3):86595.
Abstract.
The Condorcet Jury Theorem states that given subjective expected utility maximization and common values, the equilibrium probability that the correct candidate wins goes to one as the size of the electorate goes to infinity. This paper studies strategic voting when voters have pure common values but may be ambiguity averse  exhibit Ellsbergtype behavior  as modeled by maxmin expected utility preferences. It provides sufficient conditions so that the equilibrium probability of the correct candidate winning the election is bounded above by one half in at least one state. As a consequence, there is no equilibrium in which information aggregates.
An earlier version with Poisson population can be found here.
Working Papers

Equilibrium Securitization with Diverse Beliefs, with M. Piccione and S. Zhang
Abstract.
We study a general equilibrium model in which securitization emerges as a consequence of the traders' diverse beliefs about the return of a risky asset. A firm can issue and sell any feasible, monotone securities backed by a risky financial asset to risk neutral traders. Prices and characteristics of securities are determined endogenously in general equilibrium. We provide a simple characterization of the equilibrium securities, and show existence and essential uniqueness of equilibrium. Under a weak restriction on the traders' beliefs, our model delivers tranching as an equilibrium outcome. We extend the model to consider pooling of assets backing the securities, the dynamics of securitization and risk averse traders.

A Regional Approach to Salience, with Y. Masatlioglu
Abstract.
We propose a novel regional preference model (RPM) where the framing of the decision problem affects the salience of a product through the region in which it lies, and the product’s salience affects the agent’s evaluation. RPM retains the key ingredients of the salient thinking model of Bordalo et al. [2013] and allows us to understand the crux of their approach. RPM also encompasses the loss aversion model of Tversky and Kahneman [1991] and the status quo bias model of Masatlioglu and Ok [2005], providing a novel connection between three prominent models. We specialize RPM to provide a behavioral foundation for the salient thinking model to highlight the salience model’s strong predictions and distinguish it from other existing models.
 Advertising with Costly Attention
[email me for a copy]
Abstract.
This paper analyzes the implications of advertising in a model where consumers optimally allocate costly attention to information about matchspecific firm quality. Consumers easily observe price but have a cost of processing information about quality, and advertisements decrease the marginal cost of acquiring this information. Firms choose both a price and an advertising level. An increase in advertising increases both own demand and total industry demand but has positive (respectively, negative) spillovers across firms with a low (respectively, high) aggregate level of advertising. In equilibrium, a small exogenous decrease in the cost of advertising has a positive impact on equilibrium advertising, demand, and price but ambiguous effects on equilibrium profit, welfare, and consumer surplus.