Prediction markets compute facts and expertise quicker that the mass media do.

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Political prediction markets react (with a small delay) to political polls &#8212-just like the political experts and the mass media do, too. Hence, in order to discover their true social utility, the prediction markets (which are tools of intelligence) should not be compared to the polls (which are just facts) but to the similar meta intelligence mechanisms (the averaged probabilistic predictions from a large panel of experts, or the averaged probabilistic predictions from the political reporters in the mass media, or else). My bet is that, in complicated situations (such as the 2008 Democratic primary), the prediction markets beat the mass media (in terms of velocity) &#8212-even though the prediction markets are not omniscient and not completely objective (but who is?).

You might remember the research article that I have blogged about:

Learning in Investment Decisions: Evidence from Prediction Markets and Polls – (PDF file) – David S. Lee and Enrico Moretti – 2008-12-XX

In this paper, we explore how polls and prediction markets interact in the context of the 2008 U.S. Presidential election. We begin by presenting some evidence on the relative predictive power of polls and prediction markers. If almost all of the information that is relevant for predicting electoral outcomes is not captured in polling, then there is little reason to believe that prediction market prices should co-move with contemporaneous polling. If, at the other extreme, there is no useful information beyond what is already summarized by the current polls, then market prices should react to new polling information in a particular way. Using both a random walk and a simple autoregressive model, we find that the latter view appears more consistent with the data. Rather than anticipating significant changes in voter sentiment, the market price appears to be reacting to the release of the polling information.

We then outline and test a more formal model of investor learning. In the model, investors have a prior on the probability of victory of each candidate, and in each period they update this probability after receiving a noisy signal in the form of a poll. This Bayesian model indicates that the market price should be a function of the prior and each of the available signals, with weights reflecting their relative precision. It also indicates that more precise polls (i.e. polls with larger sample size) and earlier polls should have more effect on market prices, everything else constant. The empirical evidence is generally, although not completely, supportive of the predictions of the Bayesian model.

polls-prediction-markets

You might also have watched Emile Servan-Schreiber&#8217-s videos. Emile is a smart man, and those videos are truly instructive.

  1. In the first part (the lecture), our good doctor Emile Servan-Schreiber sold the usual log lines about the prediction markets &#8212-blah blah blah blah blah.
  2. In the second part, Emile Servan-Schreiber took questions from the audience in the room. &#8220-Aren&#8217-t political prediction markets just following the polls?&#8221-, asked one guy. Emile&#8217-s answer was long and confused. However, in my view, Emile actually did answer that question (before it was ever asked) in his preceding lecture when, at one point, he made the point that the media were slower than the prediction markets to integrate all the facts about the 2008 Democratic primary, around May 2008. That is the right answer to give to a conference attendee who enquires about prediction markets &#8220-following&#8221- the polls. Both the mass media and the prediction markets do follow the polls (since the polls are facts that can&#8217-t be ignored), during political campaigns. Let&#8217-s compare the prediction markets with the mass media, instead, and let&#8217-s see who&#8217-s quicker to deliver the right intelligence..

Lance Fortnow gives a good insight about the relationship between polls and prediction markets (see his last paragraph).

Yesterday the Electoral College delegates voted, 365 for Barack Obama and 173 for John McCain. How did the markets do?

To compare, here is my map the night before the election and the final results. The leaning category had Obama at 364. The markets leaned the wrong way for Missouri and Indiana, their 11 electoral votes canceling each other out. The extra vote for Obama came from a quirk in Nebraska that the Intrade markets didn&#8217-t cover: Nebraska splits their votes based on congressional delegations, one of which went to Obama.

Indiana and Missouri were the most likely Republican and Democratic states to switch sides according to the markets, which mean the markets did very well this year again. Had every state leaned the right way (again), one would wonder if the probabilities in each state had any meaning beyond being above or below 50%.

Many argue the markets just followed the predictions based on polls like Nate Silver&#8217-s fivethirtyeight.com. True to a point, Silver did amazingly well and the markets smartly trusted him. But the markets also did very well in 2004 without Silver. [Chris Masse’s remark: In 2004, Electoral-Vote.com (another poll aggregator) was all the rage.] One can aggregate polls and other information using hours upon hours of analysis or one can just trust the markets to get essentially equally good results with little effort.

The polls are facts. Prediction markets are meta to facts. Prediction markets are intelligence tools. Let&#8217-s compare them with similar intelligence tools.

Lance Fortnow&#8217-s post attracted an interesting comment from one of his readers:

to provide an exciting collection of political and other prediction markets.

These markets are as much a &#8220-prediction&#8221- tool as a wind vane or outdoor thermometer are. They moved up and down according to the daily trends, with very little insight of the longer place phenomena underlying them.

When the weather was hot (Palin&#8217-s nomination announcement) the market swinged widely towards McCain, while ignoring the cold front on the way here (the economic recession + Palin inexperience).

The value of weather forecast is in telling us things we didn&#8217-t know. We don&#8217-t need to trade securities to believe that if McCain is closing on the polls then his chances of wining are higher (duh!), which is what the markets did. We need sophisticated prediction mechanisms to tell us how the worsening economic conditions, the war in Iraq and Palin ineptitude (which in pre-Couric days wasn&#8217-t as well established) will impact this election, today poll&#8217-s be damned.

Looking at the actions by the republican teams, who were trying to read past the daily trend all the way to November 4th, it is clear that they thought all along they were losing by a fair margin. Because of this is they choose moderate, maverick McCain, went for the Palin hail mary fumble^H^H^H^H^H pass and the put-the-campaign-on-hold move.

A full two weeks before the election the McCain team concluded the election was unwinnable, while the electoral college market was still giving 25-35% odds to McCain.

As highlighted in bold, the commenter says two things:

  1. The prediction markets are just following the polls.
  2. The prediction markets have a minimal societal value.

My replies to his/her points:

  1. That&#8217-s not the whole truth. The polls are just a set of facts, whereas the prediction markets are intelligence tools that aggregate both facts and expertise. The commenter picks up a simple situation (the 2008 US presidential election) where, indeed, anybody reading the latest polls (highly favorable to Barack Obama) could figure out by himself/herself what the outcome would be (provided the polls wouldn&#8217-t screw it).
  2. That&#8217-s true in simple situations, but that&#8217-s wrong in complicated situations (such as the 2008 Democratic primary).

The emergence of the social utility of the prediction markets will come more clearly to people once we:

  1. Highlight the complicated situations-
  2. Code the mass media&#8217-s analysis of those complicated situations, and compare that with the prediction markets.

APPENDIX:

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Are prediction markets useful?

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According to Alan Abramowitz, John Tierney has been &#8220-greatly exaggerating the accuracy of the betting markets.&#8221- &#8220-They follow the polls. That’s it.&#8221-

My comment to Alan Abramowitz and John Tierney:

&#8220-They follow the polls. That’s it.&#8221-

Yes, they follow the polls. No, that&#8217-s not it.

Traders also dig the news of the day and make anticipations about the outcome. For instance, towards the end of the 2008 Democratic primary, the polls and the mass media were still giving Hillary Clinton a very good standing, whereas the prediction markets (informed by a bunch of political experts who did the counting of the delegates and super-delegates) were telling us that she was as toasted as Lehman Brothers in the middle of the credit crunch crisis.

Are prediction markets useful? If John Tierney wants to answer this question, he should pick up a prediction market and put it in the social context of that day. Some prediction markets are more useful than others. In the case of the 2008 Democratic primary (a complicated matter), the prediction markets sided with the best informed political experts against the mass media and the polls. So to speak, they were an umpire. In that case, we see the emergence of a social utility. We now have the case for the media citing more the probabilities of the liquid (play-money and/or real-money) prediction markets.

Previously: #1 – #2 – #3 – #4 – #5

External Link: Club of Growth

Intrade 2008.PRES.McCAIN > PRESIDENT.REP2008

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How frequent are arbitrage opportunities such as the following?

In addition to title, the reverse is true of OBAMA/DEM.

Do traders really think there&#8217-s some probability of McCain being elected as an idependent and Obama being replaced as the Democrat nominee?

2008 US Elections Prediction: John McCain is now the favorite at InTrade, while all the other prediction exchanges still have Barack Obama ahead. Is InTrade quicker to incorporate the latest polls because of the bigger liquidity of its prediction markets?

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#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&#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.

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.

Multi-millionaire, Republican, professor of economics Greg Mankiw uses Jason Ruspinis tax prediction markets at InTrade to assess the probability that a hypothetical John McCain presidency starting in 2009 assumes a raise in federal taxes.

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Via Marginal Revolution

P(tax hike / McCain) = 74%.

APPENDIX: Robin Hanson does not know yet who he is going to vote for, in November 2008&#8230- and feels that no scholar can help him.

2008 US ELECTORAL MAP PREDICTION: The 2008 US elections thru the prism of the prediction markets – 2008 US presidential and congressional elections – US President Prediction + US Congress Prediction – Barack Obama vs. John McCain

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#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&#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.

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.

Prediction Markets for the 2008 Electoral College = US Electoral Map

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Interesting blog post from Lance Fortnow on the VP prediction markets. (I will soon blog about those.)

InTrade – Electoral Markets Map

Their brand-new widget:

The vetting of the many potential Democratic vice president nominees was not as secretive as I thought. – Bo Cowgill was right, in hindsight.

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The New York Times has a recount on how Barack Obama reached his decision on Joe Biden. The final decision was probably made 10 days ago, while Barack Obama was vacationing in Hawaii.

[…] Mr. Obama’s decision had as much to do with Mr. Biden’s appeal among white working-class voters and compelling personal story, and his conclusion that the Delaware senator was &#8220-a worker.&#8221-

The important information in the NYT piece is that Barack Obama personally called governor Bill Richardson &#8220-late last week&#8221- to announce him that he was not considered anymore. That&#8217-s around the time the Joe Biden rumor began to have more weight in the media circles &#8212-see the InTrade chart below.

Bo Cowgill, back in May 2008 (when I started to act as a prophet of doom):

This is dumb. Cover them if something interesting happens. Maybe your theory will turn out to be wrong. Anyhow: Although the decision is made in secrecy, the Presidential nominees have a number incentives which we have plenty of information about. Specifically:
* They want someone who will balance their tickets in terms of geography, race and class.
* They want someone who will help with weak areas of their campaigns.
* They want someone who will be a good campaign surrogate — giving good speeches and attacking the opponents effectively.
* They want to avoid a VP who will de-motivate or offend the base.
* They want to avoid someone with a bunch of skeletons in the closet such as angry ex-wives, out-of-wedlock kids, etc.
* Etc etc.
Anyhow, I don’t see any reason to ignore these markets in case something interesting happens. I read Midas Oracle so that I don’t *have* to read a whole bunch of other websites!

Bo Cowgill was on the right track, now that I think of it &#8212-in a society where everything leaks out.

On the opposite of the spectrum, Tom Snee was too much extreme in his view:

According to Tom Snee of the Iowa Electronic Market, at Iowa University, futures markets need more hard information than they get in the veepstakes, to reliably predict a result.

Markets are very good at predicting elections, he says – but not choices being made inside Barack Obama&#8217-s or John McCain&#8217-s head.

Justin Wolfers was more measured.

So, Bo Cowgill and Justin Wolfers are the winners, on that one.

I was partially wrong. I am a bit too extreme, sometimes. (Did someone else notice that? :-D ) I need to learn more about&#8230- granularity.

PS: On the Republican side, now&#8230-

Price for 2008 Republican VP Nominee (others upon request)(expired at convention) at intrade.com

Who will be the Republican Vice Presidential Nominee?

Never trust a politician.

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Barack Obama + Joe Biden – THE PREDICTION MARKETS NAILED IT… triple alas (for my reputation as a world-wide prediction market pundit, and for the debate on the different quality of the various primary indicators out there).

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“Friend &#8212- I have some important news that I want to make official. I’ve chosen Joe Biden to be my running mate.”

Some blogger says his wife is fantastic.

New York Times portrait of Joe Biden.

UPDATE: Barack Obama&#8217-s speech + Joe Biden&#8217-s speech

I think it is the worst pick ever. What a blunder. Joe Biden (a D.C. insider) is unpopular and gaffe prone. Plus, that choice shows that Barack Obama is insecure when it comes to foreign policy. An emphasis on the economy and, thus, on a successful gubernatorial experience would have been better.

Kathleen Sebelius was the one to pick. She is my vice president. (And Ron Paul is my president. :-D )

I have over-estimated the secretiveness of Barack Obama&#8217-s decision process. The chart above obviously shows that the Joe Biden narrative leaked out to reporters was beamed out for a purpose: testing the Obama-needs-a-VP-who-is-strong-in-foreign-policy argument, and letting the Press do the final vetting on gaffe-prone Joe Biden.

InTrade CEO John Delaney (along with the HubDub and BetFair people) will now brag on his marketing material that his prediction exchange did forecast Joe Biden as the Democratic vice president nominee.

What&#8217-s bad in all that (other than I have an egg on my face [*] ) is that we won&#8217-t have a public debate on the different quality of the various primary indicators, and how that conditions the accuracy of the prediction markets.

[*] I have an egg on my face, but Caveat Bettor has a whole omelet on his. :-D