–
Previously: About Justin Wolfers’-s column
Justin Wolfers’- Freakonomics post (which suggests that BetFair would have a better predictive power if US traders could use it).
Justin Wolfers gives his views about the (now past) differences between the probabilistic predictions given by InTrade on the 2008 US presidential elections…- and the ones generated by the other real-money and play-money prediction exchanges. One hypothesis: US political insiders can’-t access BetFair, legally, and thus can’-t arbitrage. (But they can trade legally on the Iowa Electronic Markets, NewsFutures, Inkling, and HubDub, one could retort.)
Emile Servan-Schreiber’-s hypothesis still holds.
Or else —-your own hypothesis is welcome.
P.S.: The latest news is that InTrade now gives Barack Obama slightly above John McCain.
Video
HubDub
Previously: About Justin Wolfers’-s column
The conversation ended up on a draw.
Robin Hanson was AWOL.
These prediction exchanges present prices as probabilities (expressed in percentages):
– HubDub
– InTrade .NET …- [*] …- would get the full point if they were to switch the label “-price”- for “-probability”- on their charts.
– NewsFutures …- gets half a point. No mention of “-probabilities”- on their charts.
– Inkling Markets …- gets a quarter of a point.
– TradeFair …- gets an honorable mention, but won’-t show its charts to the non-registered public. 
[*] Which prefigures what InTrade .COM is going to be, soon, if I understood well my Deep Throat’-s tip.
As for the ultra innovative YooPick, is it yet another case of “-do what I say, not what I do“-?…- 
APPENDIX: Lance Fortnow is PMA compatible:
–
UPDATE: See the comments…-
–
UPDATE:
Nigel Eccles:
There was a bug in that chart which is now fixed. However the excess volatility is still there. The problem is that our early markets were created with a liquidity parameter which was too low. That is fixed with more recent markets. However we are also looking at modifying the MSR in some significant ways.
–
Previously:
– the latest InTrade predictions
– Emile Servan-Schreiber’-s post on market arbitrage
As I write this, Intrade gives the advantage to McCain over Obama and has the Republican party even with the Democratic party to win the election, whereas all the other prediction markets, meaning IEM, Betfair, and the NewsFutures play-money kind still favor a Democrat in the White House. That disconnect prompted Chris to wonder aloud whether Intrade is faster than the other markets to incorporate the latest polls, perhaps because of its “-bigger liquidity”-.
That’-s an interesting reaction on several levels.
First, reactivity and accuracy are not to be confused for one another. Given that market prices are supposed to be more accurate and more stable that fickle U.S. raw polls (Berg et al, 2008), one should not necessarily be impressed by the market that is quickest to mirror the latest polls. I very much doubt that traders in the “-other”- markets have not heard about the latest polls giving McCain an edge. Rightly or wrongly – it is too soon to tell – they just gave those polls less weight that the Intrade traders apparently did.
Second, the argument from “-bigger liquidity”- is not receivable. Recently, Paul Tetlock analyzed Tradesports data in depth and found that more liquidity may in fact make the market dumber. He concludes: “-In both sports and financial prediction markets, the calibration of prices to event probabilities does not improve with increases in liquidity- and the forecasting resolution of market prices actually worsens with increases in liquidity.”-
My personal theory is that Intrade has a hair-trigger Republican bias which is not found in the other markets, because Intrade appeals to, and is marketed to, the more Republican-leaning segments of the U.S. population. In my opinion, the Intrade/Tradesports Republican bias was already evident in the 2004 election, as this analysis shows.
Of course, I may be completely wrong. In any case, I find today’-s dual disconnect between the polls and most of the markets, on the one hand, and between Intrade and the other markets, on the other hand, to be two very interesting data points that should be duly recorded so we can come back to them later, with hindsight.
–
#1. Explainer On Prediction Markets
–
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…- Intelligence in, intelligence out…-
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.
–
More Info:
– The Best Resources On Prediction Markets = The Best External Web Links + The Best Midas Oracle Posts
– Prediction Market Science
– The Midas Oracle Explainers On Prediction Markets
– All The Midas Oracle Explainers On Prediction Markets
–
–
#2. Probabilistic Predictions = Charts Of Prediction Markets
–
Put your mouse on your selected chart, right-click, and open the link in another browser tab to get directed to the prediction market page of your favorite exchange.
–
–
2008 US Elections
–
–
InTrade
–
2008 US Electoral College
2008 Electoral Map Prediction = InTrade – Electoral College Prediction Markets = Probabilistic predictions for the 2008 US presidential elections based on market data from InTrade Ireland = electoralmarkets.com
–
– This is a dynamic chart, which is up to date. Click on the image, and open the website in another browser tab to get the bigger version.
–
#1. Explainer On Prediction Markets
–
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…- Intelligence in, intelligence out…-
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.
–
More Info:
– The Best Resources On Prediction Markets = The Best External Web Links + The Best Midas Oracle Posts
– Prediction Market Science
– The Midas Oracle Explainers On Prediction Markets
– All The Midas Oracle Explainers On Prediction Markets
–
–
#2. Probabilistic Predictions = Charts Of Prediction Markets
–
Put your mouse on your selected chart, right-click, and open the link in another browser tab to get directed to the prediction market page of your favorite exchange.
–
–
InTrade
–
2008 US Electoral College
2008 Electoral Map Prediction = InTrade – Electoral College Prediction Markets = Probabilistic predictions for the 2008 US presidential elections based on market data from InTrade Ireland = electoralmarkets.com
–
– This is a dynamic chart, which is up to date. Click on the image, and open the website in another browser tab to get the bigger version.
