Vickrey Auction, explained.
A Vickrey auction is a sealed-bid second-price auction: the highest bidder wins and pays the second-highest bid under the standard single-item rules.
Why it happens
Your bid decides whether you win; rivals' bids set the price. Under private values and the usual assumptions, truthful bidding avoids winning above your value or missing a purchase below it. These properties depend on the auction design.
William Vickrey analyzed auctions in which the highest bidder wins but pays the second-highest bid. Under private-value assumptions, bidding your value is weakly dominant.
Read the result
Hold rival bids fixed while changing your bid. Notice that raising an already winning bid need not increase the payment, while bidding beyond your value can make a loss possible.
A worked example
A bidder values an item at 80
The strongest rival bid is 60. A truthful bid of 80 wins at a payment of 60.
If the strongest rival instead bids 90, bidding 100 would win but require paying 90 for an item worth only 80 to this bidder.
The second-price rule separates the winning threshold from the price and makes overbidding risky.
OPTIONAL DEEPER DETAILGo deeper: inside the model
Inside this model
You win only when your bid exceeds the rival maximum; ties go to the rival. Second-price utility is value−rival if you win, otherwise zero. First-price utility is value−bid if you win. Rivals are held fixed while your bid changes.
Where this idea is useful
A practical use
Auction rules can make truthful reporting more attractive, rather than relying on bidders to volunteer private information.
A common misconception
“A higher winning bid always means a higher payment.”
In this auction, the payment is determined by the strongest competing bid, provided the auction follows the stated rules.
What this explanation leaves out
- The result assumes independent private values, no collusion, no budget constraint and no effect of losing on utility. It does not transfer unchanged to common-value auctions.
Does truthful bidding remain best in every auction?
No. The result belongs to a specific private-value second-price setting. Common values, budgets, collusion, multiple items, and different payment rules can change the incentives.
Does your bid determine the price, the allocation, or both?
Associated thinkers
Further reading
Explore the original research or the teaching reference behind this experiment.