Vickrey's second-price auction made honesty the winning bid

In 1961 William Vickrey analyzed auction formats and introduced the second-price sealed-bid auction, later named after him. At the time, auction theory was barely a field, and the standard intuition was that sellers should push buyers to pay as much as possible—which only encourages buyers to hide their true valuations.

Vickrey flipped the incentive: the winner pays the second-highest bid, not their own. If you bid above your true value you risk winning at a loss; if you bid below it you risk losing an item you would have happily bought. The only strategy that is always safe is to bid exactly what the item is worth to you.

The result is that truthful revelation is a dominant strategy, the good goes to the bidder with the highest valuation, and that bidder pays the opportunity cost—the value the second-highest bidder would have created. Vickrey showed this and the English auction are strategically equivalent, and that all four classic auction formats yield the same expected revenue under symmetric independent valuations, the revenue equivalence theorem.