In a plurality-rule election, a group of voters must coordinate behind one of two challengers in order to defeat a disliked status quo. Departing from existing work, the support for each challenger must be inferred from the private observation of informative signals. The unique equilibrium involves limited strategic voting and incomplete coordination. This is driven by negative feedback: an increase in strategic voting by others reduces the incentives for a voter to act strategically. Strategic-voting incentives are lower in relatively marginal elections, after controlling for the distance from contention of a trailing preferred challenger. A calibration applied to the U.K. General Election of 1997 is consistent with the impact of strategic voting and the reported accuracy of voters' understanding of the electoral situation.

This paper studies collective-action games in which the production of a public good requires teamwork. A leading example is a threshold game in which provision requires the voluntary participation of m out of n players. Quantal-response strategy revisions allow play to move between equilibria in which a team successfully provides, and an equilibrium in which the collective action fails. A full characterization of long-run play reveals the determinants of success; these include the correlation between players' costs of provision and their valuations for the good. The addition of an extra "bad apple" player can "spoil the barrel" by destabilizing successful teams and so offers a rationale for limiting the pool of possible contributors.

We propose a framework for analyzing transformations of demand. Such transformations frequently stem from changes in the dispersion of consumers' valuations, which lead to rotations of the demand curve. In many settings, profits are a U-shaped function of dispersion. High dispersion is complemented by niche production, and low dispersion is complemented by mass-market supply. We investigate numerous applications, including product design; advertising, marketing and sales advice; and the construction of quality-differentiated product lines. We also suggest a new taxonomy of advertising, distinguishing between hype, which shifts demand, and real information, which rotates demand.

Firms selling multiple quality-differentiated products frequently alter their product lines when a competitor enters the market. We present a model of multiproduct monopoly and duopoly using a general “upgrades” approach that yields a powerful analytical framework. We provide an explanation for the common strategies of using “fighting brands” and of product line “pruning.” The optimal strategy depends on whether entry prompts an incumbent to expand or contract its total output. We also present a general condition that guarantees that a monopolist will sell but a single product. Our model addresses other issues, including intertemporal price discrimination and “damaged goods.”