Zweitpreisauktionen

Zweitpreisauktionen, also known as Vickrey auctions, are a type of auction where the highest bidder wins the item but pays the price of the second-highest bid. This mechanism is designed to encourage bidders to reveal their true valuations of an item. In a second-price auction, a bidder's dominant strategy is to bid their true value. If they bid higher than their true value, they risk winning the auction and having to pay more than the item is worth to them if the second-highest bid is above their true value but below their bid. If they bid lower than their true value, they risk losing the auction to someone else who would have bid less than their true value, but more than the second-highest bid.

The Vickrey auction is a theoretically efficient mechanism because it leads to a truthful revelation of preferences. The winner is the bidder with the highest valuation, and the price paid is the marginal value of that bidder to the other participants. This means the item goes to the person who values it the most, and the price paid reflects the opportunity cost of that item not going to the second-highest bidder.

These auctions are often used in online advertising, where advertisers bid on keywords, and the highest bidder wins the advertising slot but pays the price of the second-highest bid. This system is also sometimes referred to as a Vickrey-Clarke-Groves (VCG) mechanism when extended to multiple items or more complex scenarios. The core principle remains the same: incentivize truthful bidding through a payment rule that depends on the bids of others.