Editing Auction (section)

===Properties of auctioned goods===
[[File:The auction in Oulu 1962 (JOKAKAL3B-12356).tif|thumb|250px|The auction in [[Oulu|Oulu, Finland]], in September 1962. Auctioneer shows a table lamp with a final price of [[Finnish markka|FIM]] 6,100.]]
[[Multiunit auction]]s sell more than one identical item at a time, rather than having separate auctions for each. This type can be further classified as either a [[uniform price auction]] or a [[discriminatory price auction]]. An example for them is [[spectrum auction]]s.

A [[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 they will pay for items A and B, but only if they get ''both''.<ref name="combinatorial">{{Citation
| last1 = Pekec
| first1 = Aleksandar
| last2 = Rothkopf
| first2 = Michael H.
| title = Combinatorial auction design
| journal = Management Science
| volume = 49
| issue = 11
| pages = 1485–1503
| date = November 2003
| doi = 10.1287/mnsc.49.11.1485.20585
| url = http://mansci.journal.informs.org/cgi/content/abstract/53/5/814
| issn = 1526-5501
| bibcode = 2003PNAS..10011153P
| access-date = 2008-06-26
| archive-date = 2007-09-11
| archive-url = https://web.archive.org/web/20070911115539/http://mansci.journal.informs.org/cgi/content/abstract/53/5/814
}}</ref> In combinatorial auctions, determining the winning bidder(s) can be a complex process where even the bidder with the highest individual bid is not guaranteed to win.<ref name="combinatorial" /> 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). [[Deferred-acceptance auction]] is a special case of a combinatorial auction.<ref>{{cite CiteSeerX |last1=Milgromy|first1=Paul|last2=Segal|first2=Ilya|title=Deferred-Acceptance Auctions and RadioSpectrum Reallocation|date=September 11, 2014|citeseerx=10.1.1.715.9582}}</ref>

Another special case of a combinatorial auction is the '''combinatorial clock auction''' (CCA), which combines a clock auction, during which bidders may provide their confirmations in response to the rising prices, with a subsequantial sealed bid auction, in which bidders submit sealed package bids. The  auctioneer uses  the final bids to compute the best value allocation and the Vickrey payments.<ref>{{cite book |last1=Bichler |first1=Martin |last2=Goeree |first2=Jacob K. |title=Handbook of Spectrum Auction Design |date=26 October 2017 |publisher=Cambridge University Press |isbn=978-1-107-13534-5 |url=https://books.google.com/books?id=QA44DwAAQBAJ&pg=PA120 |access-date=22 October 2020 |language=en}}</ref><ref>{{cite journal |last1=Ausubel |first1=Lawrence M. |last2=Baranov |first2=Oleg |title=A Practical Guide to the Combinatorial Clock Auction |journal=The Economic Journal |date=1 October 2017 |volume=127 |issue=605 |pages=F334–F350 |doi=10.1111/ecoj.12404 |s2cid=26571660 |url=https://academic.oup.com/ej/article-abstract/127/605/F334/5069450 |language=en |issn=0013-0133}}</ref>

[[Generalized first-price auction]]s and [[Generalized second-price auction]]s offer slots for multiple bidders instead of making a single deal. The bidders get the slots according to the ranking of their bids. The second-price ruling is derived from the [[Vickrey auction]] and means the final deal sealing for the number one bidder is based on the second bidder's price.