This paper adds two elements to a standard model of monopolistic competition: First, the number of potential entrants is limited in each period and increases only over time. Second, the potential entrants differ with respect to the consumers' valuation of the variant they could offer. It is...

Online advertising accounts for almost 9 percent of all advertising in the United States. This share is expected to increase as more media is consumed over the internet and as more advertisers shift spending to online technologies. The expansion of internet-based advertising is transforming the...