Rational herd behavior and informationally efficient security prices have long been considered to be mutually exclusive but for exceptional cases. In this paper we describe conditions on the underlying information structure that are necessary and sufficient for informational herding. Employing a...

I formulate a stylized Glosten-Milgrom model of financial market trading in which people are allowed to time their trading decision. The focus of the analysis is to understand people’s timing behavior and how it affects bid- and offer-prices and volume. Assuming heterogeneous quality of...

We study the effect of stochastically delayed communication on common knowledge acquisition (common learning). If messages do not report dispatch times, communication prevents common learning under general conditions even if common knowledge is acquired without communication. If messages report...

We show by example that communication can generate a failure of common knowledge acquisition. In the absence of communication, agents acquire approximate common knowledge of some parameter, but with communication they do not.

We consider a standard social choice environment with linear utility and one-dimensional types. We show by counterexample that, when there are at least three physical alternatives, Bayes-Nash Incentive Compatibility (BIC) and Dominant Strategy Incentive Compatibility (DIC) need no longer be...

We consider a framework in which each individual has his/her own concept of fairness and a social planner chooses an allocation that everyone feels fair. We say that an allocation is subjectively envy-free if no one envies the well-being of others under the allocation. We show that the...

A definition of uncertainty or ambiguity aversion is proposed. It is argued that the definition is well-suited to modelling within the Savage (as opposed to Anscombe and Aumann) domain of acts. The defined property of uncertainty aversion has intuitive empirical content, behaves well in specific...

We develop a financial market trading model in the tradition of Glosten and Milgrom (1985) that allows us to incorporate non-trivial volume. We observe that in this model price volatility is positively related to the trading volume and to the absolute value of the net order flow, i.e. the order...

Why are some cities specialised and others diversified? What are the advantages and disadvantages of urban specialisation and diversity? To what extent does the structure of cities, and the activities of firms and people in them, change over time? How does the sectoral composition of cities...

A competitive economy is studied in which sellers offer alternative direct mechanisms to buyers who have correlated private information about their valuations. In contrast to the monopoly case where sellers charge entry fees and extract all buyers surplus, it is shown that in the \emph{unique}...