Handbook of Media Economics, vol 1A

that these two firms operate in a two-sided market, with publishers and advertisers as two

distinctly different groups of consumers. They apply a calibration technique to reveal

critical and actual loss, and therefore do not have any information about demand. In line

with what we explained when comparing Equations

(6.8) and (6.4), they find that apply-

ing a Lerner index from one side of the market could be quite misleading. They claim that

in this particular case it would lead to a too narrow market definition to only consider one

of the sides of the two-sided market. Given the competition authorities’ focus on market

definition and market shares, this might lead to type I errors (banning welfare-enhancing

mergers).

Google’s acquisition of DoubleClick ...