From its early days, the World Wide Web space has demonstrated strong agglomeration trends with a very small number of web sites capturing the larger part of the Internet population. At a first glance, agglomeration over the virtual space sounds as a paradox. Web sites are numerous and highly...

Buyers' search behaviors on electronic markets are characterized by two distinctive features: i) diminishing search costs and ii) the use of informational intermediaries such as price comparison agents (shopbots). We build a simple agent-based model that captures these two features, and we use...