There are many variations on this auction system. Sometimes, the reserve price is not revealed. Also, bids may be made with
signals instead of being called out. Such signals can include tugging an ear or raising a bidding paddle. Another variation on the English auction is the open-exit auction, where the bidders must announce that they are dropping out of the bidding and they cannot re-enter. In
France, when the last bid has been made in an auction for an art object, a representative of the
state can say "Préemption de l'état" ("Pre-emption of the state") and buy the object for the highest bid. Some
housing cooperatives similarly allow members of the cooperative to pre-empt any buyer of a house constructed by the cooperative.
Scottish auction In a Scottish auction (or also time-interval auction), all bidding should be completed within a certain time interval. This ruling provides the bidders an appropriate amount of time for consideration. Speed is not important in this type of auction.
Candle auction A
candle auction is a variation in which the end of the auction is signaled by the expiration of a
candle flame. This was intended to ensure that no one could know exactly when the auction would end and make a last-second bid.
Japanese auction A
Japanese auction is a variant in which the current price changes continuously according to the auctioneer's clock, rather than by bidders' outcries. Bidders can only decide if and when to exit the arena. At first glance, this seems equivalent to English auction: apparently, in an English auction, it is a dominant strategy for each buyer whose price is above the displayed price, to always bid the minimal allowed increment (e.g. one cent) above the displayed price, so the price should increase continuously. However, in real-life English auctions,
jump bidding is often observed: buyers increase the displayed price much more than the minimal allowed increment. By its nature, jump-bidding is not possible in a Japanese auction. This may be seen as either an advantage or a disadvantage of the English auction format.
Selling more than one item The English auction has variants for selling multiple identical items or multiple different items.
Vickrey auction Vickrey auction is also known as second-price sealed-bid auction. None of the bidders know what the other is offering. The bidder with the highest price wins, but only pays the value of the next highest bid. The most important feature of these auctions is that each bidder's winning strategy is to bid according to their true valuation of the item; this auction mechanism is thus
incentive-compatible. It is also a
Pareto efficient allocation mechanism. ==References==