jackman.stanford.edu/blog
• Bayesian Analysis for the Social Sciences Wiley; Amazon; errata as of 4/16/13
• 113th U.S. Senate
• ideal point estimates pdf csv 5/15/13
• scatterplot against 2012 Obama vote share pdf
• roll call object: RData
• 113th U.S. House
• ideal point estimates pdf csv 5/17/13
• scatterplot vs Obama vote share pdf svg
• roll call object: RData
• 2013 Australian Federal Election, betting market summary
AgencyALPCoalitionProb ALP Win (%)Last 7 days
Centrebet8.501.0611.1
sportsbet8.001.0511.6
Tom Waterhouse8.001.0511.6

## Wednesday May 1, 2013

Filed under: Australian Politics — jackman @ 6:19 pm

I’m in Sydney this week prepping for TEDxSydney this weekend, which should be a blast. I’m talking about Politics and the Data Revolution, which will take in a review of some of the ways that the Data Revolution is reshaping political science research — and in particular — making that research incredibly relevant to real-world politics and policy making.

Its a very different kind of talk to lecturing, workshops, or even general audience talks. I’m learning a lot about those other, more conventional modes of giving talks from the prep I’m having to put into being comfortable with the TED format. We’ll see how it goes…

The Guardian Australia announced that I’ll be helping out with their election coverage ahead of the election here in September. It looks like a great group of people they’ve assembled (only one or two I knew about until today’s announcement).

And it seems only a month ago that I blogged about Labor’s price breaking new records for long-odds in the Australian political betting markets, at 7.30 to 1.10 on Centrebet on March 29. Think again.

Its May 2 and Labor’s out to 8.80 at Centrebet, the Coalition in to 1.05. The implied probability of a Labor win is 10.7%. Tom Waterhouse has the Coalition at 1.10.
Do ya best.

And, one of the best parts of a week in Sydney is that I usually treat myself to a workspace with a view like this:

Not too shabby.

## Monday April 8, 2013

Filed under: politics — jackman @ 5:58 pm

After a bit of a hiatus, I’ve got the 113th U.S. Senate ideal points up and running. Links to deliverables appear above, in the blog header. It is interesting to ask where the new faces line up.

Quelle surprise, there is no partisan overlap in the estimated ideal points. Manchin is the most conservative Democrat, followed by McCaskill; Collins the most liberal Republican, followed by Murkowski.

I was a little surprised to see Flake (R-AZ) and Coburn (R-OK) not out in the extreme of the Republican ideal points, but maybe thats because I’ve been traumatized by their assaults on political science.

Warren’s (D-MA) voting history places her just a little to the left of the median Democratic senator, right next to Richard Blumenthal (CT), Tammy Baldwin (WI) and Ben Cardin (MD).

Boxer is a little to the left of Feinstein, but we’re estimating those ideal points rather imprecisely (we’re not seeing a lot of roll calls that split the Democrats).

PNG version of the distribution of ideal points:

I’ve also plotted ideal points against Obama vote share in the state in the 2012 presidential election:

The separation by party is (as usual) the most compelling feature of the data. As she was in the 112th, Murkowski is decidedly more liberal than we’d expect from a Republican senator representing a state in which Obama got 40% of the vote.

Durbin and Menendez are the 2 biggest “more liberal than expected” residuals on the Democratic side; Kerry and the two DE senators (Carper and Coons) are substantially more conservative than we’d expect, given that Obama won 60% of the vote in their respective states. In Kerry’s case we’ve got a truncated voting history given his elevation to SecState, but it will be interesting to see where the DE senators wind up.

## Monday April 1, 2013

Filed under: politics,statistics — jackman @ 12:18 pm

“I needed to learn how to be persuasive. I needed to learn how to win arguments. And so I did two things.”

“I took a ton of statistics classes…”

“And I enrolled in the Ethics in Society Honors program.”

## Saturday March 30, 2013

Filed under: Australian Politics — jackman @ 6:40 am

Labor’s price is out past $7.00, the Coalition in to under$1.10. The implied probability of a Labor win is under 13%, once you factor out the bookies’ profit margins.

In the 6 years I’ve been watching the national-level betting markets, I think this is as lop-sided a market as I’ve seen. Some state-level markets have exceeded this, from memory (I haven’t been logging those prices), but I think I’m correct in asserting \$7.00+ prices are new territory for the national betting markets.

The 10 highest Labor prices I’ve recorded:

The 10 highest Coalition prices aren’t as lop-sided, and almost all date back to the 2007 election:

July 2011 to the present, implied probability of a Labor win, based on the prices offered by some of the better known betting agencies:

## Wednesday March 20, 2013

Filed under: ANES,politics,statistics — jackman @ 12:17 pm

The Senate just adopted Coburn’s (amended) amendment:

To prohibit the use of funds to carry out the functions of the Political Science Program in the Division of Social and Economic Sciences of the Directorate for Social, Behavioral, and Economic Sciences of the National Science Foundation, except for research projects that the Director of the National Science Foundation certifies as promoting national security or the economic interests of the United States.

Barbara Mikulski accepted the terms of the amendment, let it go through on the voices.

Nicely wedged, nicely played.

A great day for IR. A bad day for the study of American politics, political methodology…etc.

The “national security” or “economic interests” tests will be an interesting thing to see play out.

Or maybe we’re all sociologists now?

## Tuesday March 19, 2013

Filed under: Australian Politics — jackman @ 10:32 pm

A look at Sportbet’s market on the Labor leadership, at least for the four leading contenders…

### why are Labor’s odds improving at Centrebet?

Filed under: Australian Politics — jackman @ 7:29 pm

There is nothing like leadership chatter to help draw some punters back to the Federal election betting market…

In particular, Labor’s price has been improving a little bit over the last 72 hours at Centrebet. At the time of writing, Labor is at 4.80 to the Coalition’s 1.17 (implied probability of ALP winning = 19.6%), in from 5.60/1.13 (16.8%) as recently as 5pm Monday March 18:

Labor had been out on 5.90 to the Coalition’s 1.12 as recently as March 12.

At sportsbet, the Labor leader market has Gillard out to 2.50, Rudd at 1.50. Factoring in the other Labor leader possibilities, this equates to a 44% chance that Rudd is leader at the next election. As recently as March 9, Rudd was at 2.35 (30% probability) and Gillard at 1.60 (44% probability).

## Friday February 1, 2013

Filed under: Australian Politics — jackman @ 6:25 pm

a bit of volatility around the time of the announcement itself, but settling down to Labor’s price easing slightly. See the graphs at the top of the blog or click on the link.

And not much action in the wake of the resignation announcements etc.

Labor at 4.05 on Centrebet to the Coalition’s 1.23, for an implied 77% probability of a Coalition win.

Stick a fork in it, I reckon. Done. And done.

## Wednesday January 2, 2013

Filed under: politics,statistics — jackman @ 7:06 am

Here are two quick looks at the roll call last night from the House of Representatives, concurring with the Senate amendments to HR8. This was the so-called Fiscal Cliff vote, roll call 659 of the 2nd session of the 112th U.S. House of Representatives.

I’ve plotted the Ayes and Noes against each representative’s “ideal point”, a summary measure of each representative’s voting history based on previous roll calls in the 112th House, usually interpreted as an estimates of each legislator’s “left-right” or liberal/conservative ideological position. Democrats are shown in blue (and cluster to the left of the graph); Republicans are in red, on the right.

Notably, Speaker Boehner voted Aye, just the 9th time he has recorded a vote in the 112th Congress, which is not unusual for Speakers. With such a short, a largely one-sided short voting history, the algorithm puts Boehner out on the right-hand tail of the ideal point distribution. Majority Leader Cantor voted Nay.

The 1st graph shows a probit curve overlaid on the points, an estimate of the probability that a legislator occupying a particular point on the left-right continuum votes for the measure. Since all but 16 Democrats voted for the measure, the curve falls as we move from left to right across the page.

The 2nd graph fits probit curves separately for each party. The interesting action is among the Republicans, with the vote cleaving Republicans 151 – 85, and largely along ideological grounds. The ideal point estimate predicts Republican voting on this measure reasonably well (AUC = .816, Brier = .166).

In addition to being a rare instance of the Speaker casting a roll call vote, it is also an even rarer case of the Speaker voting against the majority of his party, including the majority leader. It might be a nice exercise to see when this last happened. We’ll see if this costs Boehner his job as Speaker; I suspect not.

## Sunday November 11, 2012

Filed under: politics,statistics — jackman @ 1:06 pm

Obama won the 2012 election by keeping the swing small where it needed to be kept small. Just two states changed hands: Indiana and North Carolina, both won narrowly by Obama in 2008.

But consider this. Florida, Ohio and Virginia were all won by Obama in 2008 on margins smaller than the 53.4-46.6 national margin. Obama kept them all in 2012, with swings smaller than the national swing. Details…

Nationally, the two-party swing against Obama is currently -2.11 percentage points: that is, Obama beat McCain in 2008 53.4-46.6; at this stage of the 2012 count he is winning 51.3-48.7.

Let’s look at some key swing states.

• Ohio (18 Electoral votes): Obama won it 52-48 in 2008 (in two-party terms). A two percent swing and Romney wins it. The swing is only -1.12, about half the national swing. Obama wins Ohio 51-49.
• Florida (29 EVs): Obama won 51.3-48.7 in 2008. A 1.3 percent swing against Obama would see the state fall to Romney. The swing appears to be -0.83 points with Obama winning 50.4-49.6.
• Virginia (13 EVs): Won by Obama 53.2-47.8. Romney needed a -3.2 percentage point swing against Obama to win the state. He got half way, -1.6 points, and the state stays with Obama.
• North Carolina (15 EVs): Obama outpolled McCain by 13,700 votes in 2008, to win 50.2-49.8. The swing was -1.26 points and Romney wins 51.1 of the two party vote.

And on it goes. Without more of these easier states coming over the line, getting to 270 was a very difficult proposition for Romney. The Romney campaign would have needed some large swings in other battlegrounds to get close.

• Iowa: Obama had a 4.7 point margin, the swing to Romney was 1.8.
• New Hampshire: 4.8 margin, a 1.9 swing.
• Colorado: a 4.4 point margin, a 2 point swing.
• Wisconsin: a 7 point margin, a 3.6 point swing (larger than the national average, and larger than the swing-state average swing, thanks Paul Ryan?).
• Nevada: a 6.3 point margin, a 3 point swing.

And Pennsylvania? Forget it. With 20 Electoral College votes you can understand why it is an enticing target. But Pennsylvania was higher up the tree than Iowa, New Hampshire or Colorado, breaking 55.2-44.8 in 2008. Romney won a 2.6 point swing in Pennsylvania (slightly higher than the nationwide swing), but still only half of what he would have needed to win the state.

Indiana was the other Romney pickup. Obama’s 50.5-49.5 victory there in 2008 was a shocker, coming on the back of 10.9 point swing: to understand how big that was, recall that the national two-party swing to Obama was 4.8 points in 2008. Indiana was never on anyone’s battleground list in 2012. Expectations were that Indiana would “revert to type”. Absent any serious attempt to defend the narrow and unexpected 2008 win from the Obama camp, Indiana swung 5.8 points in 2012 (more than twice the national swing) with Romney winning 55.3-44.7.

A similar logic applies to Missouri, which Obama almost won in 2008, falling short by 0.06 of a percentage point, outpolled by McCain by just 3,600 votes. Missouri “reverted to type” in 2012 too, with a 4.8 point swing. In fact, Obama’s 2012 showing is worse than Kerry’s in 2004 (45.1% of the two party vote, versus Kerry’s 46.3%).

Two graphs summarize all this; clicking on each will open a larger version in a new browser window.

The first is a dot plot showing the swings in order. The color shows the disposition of the state in 2008. Two vertical bars show the national swing and no swing. Open plotting symbols for swing states show the swing they would have required to change hands: for North Carolina, the open plotting symbol lies to the right of the actual swing (the swing exceeded Obama’s 2008 margin). Again, note how the swings against Obama come up short in the other battleground states.

Second, a plot of 2012 swing against 2008 result. Shaded regions denote politically distinct regions: (1) Obama retains, where the 2012 swing isn’t enough for the state to fall to Romney, with 27 states in this category; (2) Obama losses, where the swing against Obama is enough for the state to fall to Romney (Indiana and North Carolina); (3) Obama gains (a null set in 2012); and (4) Republican retains, with 22 states in this category. The District of Columbia is excluded from this graph. The size of the plotting symbol is proportional to the state’s Electoral College votes; color indicates 2012 disposition; the national result is shown with a dark point labelled “USA”.

Obama wins the election on the back of that set of states that sit just to the right of the 50-50 threshold on the horizontal axis, but that didn’t drift down on the vertical “swing” dimension into the “change hands” cone.

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