PredictWise Blog

Possible error in Scottish predictions really large and likely favors NO

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Using betting market data from Betfair, I have the NO vote in the Scottish independence election at 84% to succeed. And, I can break that down:

6% for 0% to 40% of the vote for YES

26% for 40% to 45% of the vote for YES

51% for 45% to 50% of the vote for YES

12% for 50% to 55% of the vote for YES

3% for 55% to 60% of the vote for YES

2% for 60% to 100% of the vote for YES

There are two key points. First, this is a really wide range. The polls are all clustered at NO being a few points ahead, but the markets are giving 32% that NO wins by 10 percentage points or more! Second, if the polls are way off, the swing is going to favor the NO vote. Intelligent review of the polls are both surmising and determining this possibility.

To provide some perspective on this crazy error possibility, let us consider what an 84% election the in US looks like right now. Gary Peters is 83% to defeat Terri Lynn Land for the open Michigan senate election. My current fundamental and poll-based forecast has Peters getting about 54% of the vote. I would put the possibility at him getting 60% approaching 0%!

Election Update - 9/17, 48 Days

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I last addressed the senate 6 days ago and there has been meaningful movement in two states. First, North Carolina has gone from leaning Democratic to strong Democratic. This is on the strength of some new polls. Second, Kansas has gone from very difficult to possible for the Democrats. That is assuming that Orman is going to caucus with the Democratic Party. This on the strength of the first polls showing the Democratic candidate basically gone and looking increasingly likely the Democratic candidate will not be on the ballot, despite the Lt. 'Governor's best efforts. It amazing to think that Kansas’ top three races: Senator, Governor, and Lt. Governor may all go Democratic.

Here is New York Times and FiveThirtyEight compared with PredictWise. Not too much difference:

Updating Predictions: senatorial, senatorial balance of power, and gubernatorial.

Election Update - 9/12, 53 Days

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There are more interesting gubernatorial elections than senatorial elections. While the immediate national stakes do not seem as high, that is a misconception in many ways. Governors such at Wisconsin’s Scott Walker (R) is one of the most influential people in the country advocating for breaking unions,  Maine’s Paul LePage (R) is not that far behind, Kansas’ Sam Brownback (R) is the poster-child for step tax cuts and austerity (which is not going well), and Florida’s Rick Scott (R) gained fame for drug testing the poor. In Arizona they are fighting over a legacy of controversial immigration policies and Georgia’s Jason Carter (D) is Jimmy’s grandson!

The most interesting races feature these influential people: GA, FL, AZ, WI, CT, ME, and KS are the core elections. I will start with ones that lean Republican. In Georgia Jason Carter is 24% to unseat Nathan Deal (R), best known nationally for Guns Everywhere Law … which Jason Carter also voter for in the state senate. The Florida election is between Rick Scott and Charlie Crist (D) the former Republican governor, who switched over in 2012. The Arizona election between Doug Ducey (R) and Fred DuVal (D) will indubitably turn on the controversial legacy of Jan Brewer (R). Wisconsin is all about Scott Walker who broke the unions and passed very harsh voting restrictions. Connecticut features incumbent Dan Malloy (D) against Thomas Foley (R). The first one that leans Democratic is Maine with Paul LePage on the ropes against Mike Michaud (D). Finally, in Kansas Sam Brownback is losing to Paul Davis (D), which would be a huge upset for both Kansas and the austerity measures that Brownback pushed as governor.

 Updating Predictions: senatorial, senatorial balance of power, and gubernatorial.

NFL Week 2

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I forgot to post this yeseterday, so I am one game short!

Election Update - 9/11, 54 Days

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I launched my state-by-state senatorial and gubernatorial predictions in the first week of August. You can find them on PredictWise updating as the data updates: senatorial and gubernatorial. Most important for the senatorial elections, you can find the expected balance of power on a separate table. I hope to add the district-by-district house election by October 1.

The method is the exact same as I described in this paper, forthcoming in the International Journal of Forecasting; with one big exception as there are no state-by-state betting markets, yet. Thus, the data is simplified to just fundamental data and polling data. The polling data, pulled from Huffington Post’s Pollster and RealClearPolitics, is transformed into an expected vote share and probability of victory using the model outlined in the aforementioned paper. I average the aggregated polling snapshots and then correct for both the anti-incumbency bias (incumbents poll too low compared to the results) and the regression to the mean (leads narrow as Election Day approaches) with a set of linear coefficients determined by past elections. The fundamental data (e.g., previous votes in the district, incumbency, and economic indicators) is transformed into an expected vote share and probability of victory using the model outlined in this paper with Patrick Hummel (forthcoming in Electoral Studies). We tested dozens of reasonable variables and used historical data to form the most efficient relationships between the fundamental data and expected outcomes.

The reason that I have not written yet on this is threefold. First, I find the fixation on the horserace months before the elections distracting. Second, I am working on a lot of other cool things! Third, the senatorial forecasts are not that much different than anyone else.

I could have gotten out dozens of small articles on the state of the senatorial election over the last few months, but, to be frank, when I contemplate politics, I prefer to focus on matters like our impending war with ISIS (or Syria) (i.e., foreign policy), the ongoing persistent, but sluggish recovery (e.g., economic policy), and major policy debates over gay marriage and gun control (e.g., social policy). We have elections to change (or preserve) policy, so it seems foolish that we focus so much time on elections and so little time on policy. Also, the fate of the senatorial elections are largely out of our hands, unless you are big investor of money (or time), but it is always meaningful to learn more about the major policy issues of the day! That brings me point two, which is a totally exciting project that I will announce in a few weeks that focuses more on sentiment and predictions around issues.

I was pretty stoked when I compiled the tables and saw that they looked pretty similar to everyone else (good sign that everything was running well), but, then again, that does not make it too meaningful to you; my senatorial forecasts just confirm what everyone else is already saying. First, binary control over the senate is incredibly close. The Republicans need 51 seats and the Democrats need 50 seats. The most likely outcome, at 21% is the Republicans getting 51 seats; they have a 60% likelihood of getting 51 or more seats. Second, I have 10 competitive races (i.e., currently between 10% and 90%): AK, AR, CO, GA, IA, KY, LA, MI, NC, and NH. The New York Times has 9 competitive races (they have Kentucky at 7% for Grimes (D) and I have her at 12%; they have New Hampshire at 9% for Brown (R) and I have him at 17%; they have Kansas at 24% for Orman (I) and I have him at 8%, but that may change once the real polling starts there and the courts rule on the fate of the Democratic candidate). FiveThirtyEight has all 11 reasonable races in the mix. Third, everyone has the same few key races: NC, AK, LA, and IA, with KS a wildcard.

Here is New York Times and FiveThirtyEight compared with PredictWise:

Tomorrow I will provide an overview of the gubernatorial elections. And, over the next few weeks I will jump into the key senatorial and gubernatorial elections in more depth, and focus on shifts in the elections as they occur.

 Updating Predictions: senatorial, senatorial balance of power, and gubernatorial.