CeDEx Discussion Paper No. 2006–06 A complete characterization of pure strategy equilibrium in uniform price IPO auctions

The focus for the Centre is research into individual and strategic decision-making using a combination of theoretical and experimental methods. On the theory side, members of the Centre investigate individual choice under uncertainty, cooperative and non-cooperative game theory, as well as theories of psychology, bounded rationality and evolutionary game theory. Members of the Centre have applied experimental methods in the fields of Public Economics, Individual Choice under Risk and Uncertainty, Strategic Interaction, and the performance of auctions, markets and other economic institutions. Much of the Centre's research involves collaborative projects with researchers from other departments in the UK and overseas. Collusive equilibria in share auctions despite being the focus of previous theoretical research, have received little empirical or experimental support. We develop a theoretical model of uniform price initial public offering (IPO) auctions and show that there exists a continuum of pure strategy equilibria where investors with a higher expected valuation bid more aggressively and as a result the market price increases with the market value. The collusive equilibria lie in fact on the boundary of this set, which is obtained under stricter conditions when demand is discrete than in the continuous format. Our results have important implications for the design of IPO auctions.