Concentration in advertising-supported online markets: an empirical approach

This paper examines the causes of market concentration in advertising-supported online markets such as sports, news, and email. In particular, it is the first paper to explore the relationship between concentration and product differentiation, economies of scale, market size, advertising, content costs, and multi-market ownership in online markets. As expected, differentiated large markets with low content costs and little multi-market ownership are less concentrated. Furthermore, I show that advertising-supported online markets have much in common with the magazine industry.