2. Introduction
• Auctions are the most widely-studied economic mechanism.
• Auctions refer to arbitrary resource allocation problems with
self-motivated participants: Auctioneer and bidders
• Auction (selling item(s)): one buyer, multiple bidders)
e.g. selling a cd on eBay
• Reverse Auction (buying item(s)): one buyer, multiple sellers
e.g. procurement
3. Auction - definitions
• An auction is a method of allocating scarce goods,
– a method that is based upon competition:
• A seller wishes to obtain as much money as possible,
• A buyer wants to pay as little as necessary.
• An auction offers the advantage of simplicity in
determining market-based prices.
• It is efficient in the sense that it usually ensures that
– resources accrue to those who value them most highly;
– sellers receive the collective assessment of the value.
• The price is set the bidders.
4. When are Auctions used?
• Auctions are useful when
– selling a commodity of undetermined quality;
– the goods do not have a fixed or determined market value, in other
words, when a seller is unsure of the price he can get.
• Choosing to sell an item by auctioning it off is
– more flexible than setting a fixed price;
– less time-consuming and expensive than negotiating a price.
• Auctions can be used
– for single items such as a work of art;
– and for multiple units of a homogeneous item such as gold or
Treasury securities.
5. Where auctions are used nowadays?
• Treasury auctions (bill, notes, Treasury bonds, securities)
• Has been used to transfer assets from public to private
sector
• Right to drill oil, off-shore oil lease
• Private firms sell products (flowers, fish, tobacco,
livestock, diamonds)
• Internet auctions
6. Prices
• The price is set not by the seller, but by the bidders.
• The seller sets the rules by choosing the type of auction
to be used.
• The auctioneer doesn't often own the goods, but acts
rather, as an agent for someone who does.
• The buyers frequently know more than the seller about the
value of the item.
7. Drawbacks of Auctions
• "Winners curse" is widely recognized as being
that phenomenon when a "lucky" winner pays
more for an item than it is worth. Auction winners
are faced with the sudden realization that their
valuation of an object is higher than that of anyone
else.
8. Bidder Valuations
• Reasons for bidding in the auction:
– a bidder wishes to acquire goods for personal consumption (wine
or art);
– a bidder wishes to acquire items for resale or commercial use.
• Private valuation
– The bidder makes his own private valuation of the item for sale.
– All bidders have private valuations and tend to keep that
information private.
9. Bidder Valuations (cont.)
• Common valuation
– An individual bid is predicated not only upon a private valuation
reached independently, but also upon an estimate of future
valuations of later buyers. Each bidder of this type tries (using the
same measurements) to guess the ultimate price of the item.
– The item is really worth the same to all, but the exact amount is
unknown
• Example
– Purchasing land for its mineral rights
• Each bidder has different information and a different valuation, but
each must guess what price the land might ultimately bring.
10. Taxonomy of Auctions
• William Vickrey [Vickrey] established the basic
taxonomy of auctions based upon the order in
which prices are quoted and the manner in
which bids are tendered. He established four
major (one sided) auction types:
– English: Ascending-price, open-cry;
– Dutch: descending-price, open-cry,
– First-price, sealed bid,
– Vickrey or second-price, sealed bid.
12. English Auction
• The English auction
– the open-outcry auction or the ascending-price auction.
• It is used commonly to sell art, wine and numerous other
goods.
• "Here the auctioneer begins with the lowest acceptable
price--the reserve price-- and proceeds to solicit
successively higher bids from the customers until no
one will increase the bid. The item is 'knocked down'
(sold) to the highest bidder.”
Paul Milgrom
13. Disadvantages of English Auction
• The key to any successful auction (from a seller's point of
view) is the effect of competition among the potential
buyers.
• In an English auction, the under bidder usually forces the
bid up by one small step at a time. Often a successful
bidder acquires an object for considerably less than his
maximum valuation simply because he need only increase
each bid by a small increment.
– the seller does not necessarily receive maximum value.
• Other auction types may be superior to the English auction
for this reason (at least from the seller's perspective).
14. Dutch Auction
• In a Dutch auction, bidding starts at an extremely high
price and is progressively lowered until a buyer claims an
item.
• When multiple units are auctioned, normally more takers
claim the item as price declines.
– The first winner takes his prize and pays his price
– Later winners pay less.
• When the goods are exhausted, the bidding is over.
15. Advantage of a Dutch Action
• In the Dutch system, if the bidder with the highest interest
really wants an item, he cannot afford to wait too long to
enter his bid.
• That means he might bid at or near his highest valuation.
• Dutch auctions are used extensively in the Netherlands to
auction flowers such as tulips.
• Car dealers sometimes use a Dutch auction to sell cars; a
price for a particular car is posted each day on a marquee,
and the price is lowered each day until someone purchases
the car
17. First Price- Sealed Bid
• Sealed (not open-outcry like the English or Dutch varieties) and
thus hidden from other bidders.
• Buyers simultaneously submit their bids
• Usually, (but not always) each participant is allowed one bid.
– Buyers’ valuations of the good unknown to each other
– Highest Bidder wins and gets the good at the amount he bid
A sealed-bid format has two distinct periods
– a bidding period in which participants submit their bids;
– a resolution phase in which the bids are opened and the winner
is determined (sometimes the winner is not announced).
18. The Vickrey Auction
• The uniform second-price auction is commonly called
the Vickrey auction.
• The bids are sealed, and each bidder is ignorant of other
bids.
• The item is awarded to highest bidder at a price equal to
the second-highest bid (or highest unsuccessful bid).
– winner pays less than the highest bid.
• Example
– Suppose bidder A bids $10, bidder B bids $15, and bidder C offers
$20, bidder C would win, however he would only pay the price of
the second-highest bid, namely $15.
19. The Vickrey Auction-Example
• Suppose you value an item at 100
• You should bid 100 for the item
• If you bid 90
– Someone bids more than 100: you lose anyway
– Someone bids less than 90: you win anyway and pay second-price
– Someone bids 95: you lose; you could have won by paying 95
• If you bid 110
– Someone bids more than 11o: you lose anyway
– Someone bids less than 100: you win anyway and pay second-
price
– Someone bids 105: you win; but you pay 105, i.e., 5 more than
what you value
20. Double Dutch Auction
• A buyer price clock starts ticking at a very high price and
continues downward.
• At some point the buyer stops the clock and bids on the
unit at a price favorable to him.
• At this point a seller clock starts upward from a very low
price and continues to ascend until stopped by a seller who
then offers a unit at that price.
• Then the buyer clock resumes in a downward direction.
• The trading period is over when the two prices cross, and
at that point all purchases are made at the crossover point.
21. Auction Strategies
• Buyers bid differently depending upon the rules of an
auction.
• A seller is faced with choosing an auction type, and so he
must predict the behavior of bidders.
• On the other hand, a bidder tries to predict the behavior of
the other bidders. Each bidder makes an estimate of his
own value of the object and also an estimate of what others
will bid on it. Good bidding is often the result of correct
predictions about the behavior of others and sometimes
that means guessing the extent of someone else's
information correctly.
22. From a Seller's Perspective
• In any auction a seller can influence results by revealing
information about the object.
• Intuitively, a bidder's profits rise when he can exploit
information asymmetries (when the bidder has information
not available to others).
• So a seller's optimal strategy is to reveal information and
to link the final price to outside indicators of value (an
authoritative evaluation).
– if a seller seems reluctant to disclose something, a buyer always
assumes the hidden information must be unfavorable.
23. English Strategy
• In a private-value English auction, a player's best strategy
is to bid a small amount more than the previous high bid
until he reaches his valuation and then stop.
• This is optimal because he always wants to buy an object
if the price is less than its value to him, but he wants to pay
the lowest possible price.
• Bidding always ends when the price reaches the valuation
of the player with the second-highest valuation.
24. Dutch Strategy
• At some point in advance, the bidder must decide the
maximum amount he will bid (the same problem as that
facing a bidder in a sealed-bid auction) .
• The decision is based upon
– his own valuation of the object;
– his prior beliefs about the valuations of other bidders.
• This auction type is strategically equivalent to first-price
sealed auction because no relevant information is disclosed
in the course of the auction, only at the end when it is too
late.
25. First Price, Sealed Bid Strategy
• It is difficult to specify a single strategy because a profit-
maximizing bid depends upon the actions of others.
• The tradeoff is between bidding high and winning more
often, and bidding low and benefiting more if the bid wins
(bigger profit margin).
• Most bidders attempt to shade their bids to move closer to
market consensus. This also helps to avoid winner's curse.
26. Vickery Strategy
• The dominant strategy for a bidder in a Vickrey (second-
price) auction is to submit a bid equal to his true
reservation price because he then accepts all offers below
his reservation bid and none that are above. (according to
Paul Milgrom)
• A participant who bids less is more likely to lose the
auction and all that strategy accomplishes is to lower the
chance of victory. Bidding high carries the risk of winner's
curse. Neither affects the price paid if he wins.
27. Vickery Strategy (cont.)
• When each bidder adopts a strategy of bidding his true
price, the outcome is that the item is awarded to the bidder
with the highest valuation at a price equal to the second
highest valuation.
• A potential drawback is that this system requires total
honesty from the auctioneer(s). If the auctioneer is not
trustworthy, he could open the bids, find the winner and
insert a new bid just barely under that to ensure higher
revenues.
28. Online Auctions
• Online auctions require the consumer (the bidder) to
manage their negotiation process.
• Optimal strategies for the main auction types are known
– can be presented in algorithmic form
• bidding can be done automatically by corresponding
agents.
• Examples of such agents
– AuctionBot
– Kasbah
– Tete-a-Tete
29. AuctionBot
• A multi-purpose internet auction server developed at the
University of Michigan.
• Two main operations you can perform with the
AuctionBot:
– start a new auction;
– bid in an existing auction.
• A user must create an AuctionBot account.
• The AuctionBot provides facilities for examining ongoing
auctions, and inspecting your own account activity.
30. AuctionBot (cont.)
• To create an auction a user needs to choose an auction
format and specify the parameters
– clearing times, methods for resolving tie bids, the number of
sellers permitted etc.,
• Buyers and sellers can than bid according to the auction
multilateral distributed negotiation protocols.
• Aucton Bot provides an API for users to create their own
software agents to autonomously compete in the Auction
Bot marketplace.
31. eBay
• Person-to-person online trading community.
• Implements selling and bidding online protocols.
• Trades in a wide variety of categories.
• Established its presence in many counties (Canada,
Germany, etc.)
• Provides the biggest consumer-to-consumer online
marketplace.
32. Conclusions
• Online auctions are becoming extremely popular because
– online auctions have wide geographic reach;
– automated negotiations are cheaper and faster.
• It is also a vibrant research area since the research on
automated negotiations and their idiosyncrasies has just
started.
