The Number of Active Bidders in Internet Auctions
Internet auctions attract numerous agents, but only a few become active bidders. Under the Independent Private Values Paradigm the valuations of the active bidders form a specific record sequence. This record sequence implies that if the number n of potential bidders is large, the number of active bidders is approximately 2logn, potentially explaining the relative inactivity. Moreover, if the arrival of potential bidders forms a non-homogeneous Poisson process due to a time preference for auctions that are soon to close, then the arrival process of the active bidders is approximately a Poisson arrival process.
De Haan, L., de Vries, C., and Zhou, C. "The Number of Active Bidders in Internet Auctions." Journal of Economic Theory, 148(4), p. 1726–1736, 2013.