We study welfare distortions in a multiproduct-firm pricing game with constant elasticity of substitution (CES) or multinomial logit (MNL) demand. Using approximations both around small market shares and around monopolistic competition conduct, we identify sufficient statistics to gauge the extent of inefficiencies caused by oligopolistic market power. We find that, at a low order, the oligopoly distortions are proportional to the Herfindahl index of industry concentration. At a higher order, distortions also depend on the cubic Hannah-Kay concentration index. Additionally, we show that the welfare loss from resource misallocation is approximately proportional to the difference between the cubic Hannah-Kay index and the square of the Herfindahl index.