OSCARS 2008: The Hollywood Stock Exchange has been more accurate than InTrade.

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&#8230- dixit James Surowiecki (commenting on Felix Salmon&#8217-s post):

Interesting. The Hollywood Stock Exchange, not surprisingly, did better [than InTrade]. Cotillard was, as at Intrade, a comfortable second favorite. But so too was Swinton &#8212- in fact, she was even more of a second favorite, as her price was very close to Blanchett&#8217-s when the market closed. In fact, if you look at her chart:
http://movies.hsx.com/servlet/SecurityDetail?symbol=A8TSW

it&#8217-s hard not to conclude that the market was really incorporating new information in the week leading up to the ceremony.

I didn&#8217-t follow the Hollywood Stock Exchange [*] (or even BetFair) closely for the Oscars 2008, but here are InTrade&#8217-s expired event derivatives (event futures):

Best Picture

Best Director

Best Actor

Best Actress

[*] UPDATE: HSX claims a 75% success rate.

Prediction markets produce dynamic, objective probabilistic predictions on the outcomes of future events by aggregating disparate pieces of information that traders bring when they agree on prices. Prediction markets are meta forecasting tools that feed on the advanced indicators (i.e., the primary sources of information). Garbage in, garbage out&#8230- Intelligence in, intelligence out&#8230-

A prediction market is a market for a contract that yields payments based on the outcome of a partially uncertain future event, such as an election. A contract pays $100 only if candidate X wins the election, and $0 otherwise. When the market price of an X contract is $60, the prediction market believes that candidate X has a 60% chance of winning the election. The price of this event derivative can be interpreted as the objective probability of the future outcome (i.e., its most statistically accurate forecast). A 60% probability means that, in a series of events each with a 60% probability, then 6 times out of 10, the favored outcome will occur- and 4 times out of 10, the unfavored outcome will occur.

Each prediction exchange organizes its own set of real-money and/or play-money markets, using either a CDA or a MSR mechanism.

Linear Programming – Combined Value Trading – Parimutuel Call Market – Combinatorial Call Markets

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David Pennock:

[…] Each order is associated with a decision variable x that ranges between 0 and 1, encoding the fraction of the order that the auctioneer can accept. There is one constraint per outcome that ensures that the auctioneer never loses money across all outcomes. The choice of objective function depends on the auctioneer’s goals, but something like maximizing the fill fraction makes sense.

Once the program is set up, the auctioneer solves for the x variables to determine which orders to accept in full (x=1), which to accept partially (0&lt-x&lt-1), and which to reject (x=0). The program can be solved either in batch mode, after waiting to collect a number of orders, or in continuous mode immediately as new orders arrive. Batch mode corresponds to a call market. Continuous mode corresponds to a continuous auction, a generalization of the continuous double auction mechanism of the stock market.

Each order consists of a price, a quantity, and an outcome bundle. Traders can just as easily bet on single outcomes, negations of outcomes, or sets of outcomes (e.g., all Western Conference NBA teams). Every order goes into the same pool of liquidity no matter how it is phrased.

Price quotes are queries to the linear program of the form “at what price p will this order be accepted in full?” (I believe that bounds on the dual variables of the LP can be interpreted as bid and ask price quotes.) […]

Go reading all the post. There is a bunch of good comments&#8230- the best was submitted by Mike Giberson&#8230-