Vickrey Auction
A sealed-bid auction where the highest bidder wins and pays the second-highest bid.
Definition
Winner: ; payment: ; all others pay .
With single-unit private values, truthful bidding is weakly dominant.
Intuition
Because price is set by others, your bid only affects whether you win, not how much you pay — so truth-telling is optimal.
Incentive compatibility means bidders do not need to strategize over others' valuations.
Worked example
Values : bidder 1 wins and pays , netting surplus .
Under symmetric IPV, expected revenue equals that of the first-price auction (Revenue Equivalence).
The math
The Vickrey auction is a special case of the VCG mechanism for a single indivisible good.
Generalizes to combinatorial settings as VCG, charging each winner their marginal externality on others.
Where it is used
Historical use in stamp auctions; conceptual basis for GSP in sponsored-search ads and many computerized markets.
Cornerstone example in mechanism-design teaching.
More in Game theory
Assembled from the ReLU.chat curated knowledge base. These explanations are concise on purpose; check the sources for anything important.