Oligopoly and welfare: A unified presentation with applications to trade and development

We develop a unified sequence of models to examine the determinants of price, output, profitability and concentration for different kinds of oligopolistic market. We relate various magnitudes of significance to judges of welfare and to policy makers, such as consumer surplus, profit, or added benefits of employment or trade surplus, to observable magnitudes such as the size and concentration of the market. It emerges that various appropriately formulated Herfindahl indices are useful in several of these relations. We attempt to present results in a way that is useful for empirical investigations and pay particular attention to applications in trade and development.