Secondary Types of Auctions

All-pay auction is an auction in which all bidders must pay their bids regardless of whether they win. The highest bidder wins the item. All-pay auctions are primarily of academic interest, and may be used to model lobbying/bribery (bids are political contributions) or competitions such as a running race.

Buyout auction is an auction with a set price (the 'buyout' price) that any bidder can accept at any time during the auction, thereby immediately ending the auction and winning the item. If no bidder chooses to utilize the buyout option before the end of bidding the highest bidder wins and pays their bid. Buyout options can be either temporary or permanent. In a temporary buyout auction the option to buy out the auction is no longer available after the first bid is placed. In a permanent buyout auction the buyout option remains available throughout the entire auction until the close of bidding. The buyout price can either remain the same throughout the entire auction, or vary throughout according to preset rules or simply at the whim of the seller.

Combinatorial auction is any auction for the simultaneous sale of more than one item where bidders can place bids on an "all-or-nothing" basis on "packages" rather than just individual items. That is, a bidder can specify that he or she will pay for items A and B, but only if he or she gets both. In combinatorial auctions determining the winning bidder can be a complex process where even the bidder with the highest individual bid is not guaranteed to win. For example, in an auction with four items (W, X, Y and Z), if Bidder A offers $50 for items W & Y, Bidder B offers $30 for items W & X, Bidder C offers $5 for items X & Z and Bidder D offers $30 for items Y & Z, the winners will be Bidders B & D while Bidder A misses out because the combined bids of Bidders B & D is higher ($60) than for Bidders A and C ($55).

No-reserve auction (NR), also known as an absolute auction, is an auction in which the item for sale will be sold regardless of price. From the seller's perspective, advertising an auction as having no reserve price can be desirable because it potentially attracts a greater number of bidders due to the possibility of a bargain. If more bidders attend the auction a higher price might ultimately be achieved because of heightened competition from bidders. This contrasts with a reserve auction, where the item for sale may not be sold if the final bid is not high enough to satisfy the seller. In practice, an auction advertised as "absolute" or "no-reserve" may nonetheless still not sell to the highest bidder on the day, for example, if the seller withdraws the item from the auction or extends the auction period indefinitely, although these practices may be restricted by law in some jurisdictions or under the terms of sale available from the auctioneer.

 Reserve auction is an auction where the item for sale may not be sold if the final bid is not high enough to satisfy the seller - that is, the seller reserves the right to accept or reject the highest bid. In these cases a set 'reserve' price known to the auctioneer, but not necessarily to the bidders, may have been set in advance below which the item may not be sold. A reserve auction is safer for the seller than a no-reserve auction as they are not required to accept a low bid, but this could potentially result in a lower final price than might otherwise be the case if this means that less interest is generated in the.

 Round robin auction is a variant of the English auction sometimes used to sell real estate. Potential buyers inspect the property, and then place bids before a certain deadline. Then each potential buyer is contacted by phone in a round robin fashion, told the highest bid to that point, and offered the chance to keep their previous bid, raise their bid, or drop out of the auction.

 Silent auction is a variant of an English auction where bids are written on a sheet of paper. At the predetermined end of the auction the highest listed bidder wins the item. This auction is often used in charity events, with many items auctioned simultaneously with a common finish time. The auction is "silent" in that there is no auctioneer, the bidders writing their bids on a bidding sheet often left on a table near the item. Other variations of this type of auction may include sealed bids. The highest bidder pays the price he or she submitted. 

 Walrasian auction or Walrasian tâtonnement is an auction in which the auctioneer takes bids from both buyers and sellers in a market of multiple goods. The auctioneer progressively either raises or drops the current proposed price depending on the bids of both buyers and sellers, the auction concluding when supply and demand exactly balance. As a high price tends to dampen demand while a low price tends to increase demand, in theory there is a particular price point somewhere in the middle where supply and demand will match.