Vickrey Auction (Second-Price Auction)

A single-item auction where the highest bidder wins and pays the highest competing bid, with truthful bidding weakly dominant under standard private-value assumptions.

In a standard sealed-bid second-price auction for one item, the highest bidder wins and pays the highest competing bid. With a known private value, quasilinear payoff, and the usual auction rules, bidding that value is weakly dominant: it does at least as well as another bid for every fixed set of competing bids.

The key is that your bid determines whether you win, while the competing bid determines what you pay. Underbidding can lose a beneficial purchase; overbidding can win at a price above your value. Ties may produce zero surplus. Interdependent values, collusion, seller manipulation, budgets, participation costs, or more complex allocation rules require additional analysis. Generalized second-price advertising auctions are not simply the same mechanism.

When to use it

Useful for studying auction design and checking claims of truthful revelation.

How it can help

Understand how separating the winning threshold from the bidder’s payment can align reporting incentives.