Inferring ascending auction participation from observed bidders

Participation in internet auctions goes well beyond those who place a bid. Participants arrive in random order, and if the auction's standing price has already exceeded a participant's valuation, she will not bid. Even so, her unreported valuation is a relevant part of demand for the item, and in an alternate random order, her bid would have been registered. I provide a method to estimate the average number of participants from the average number of bidders per auction. This enables estimation of the distribution of participant valuations from either the distribution of closing prices or the distribution of all observed bids.