Sunday, May 22, 2011


Institutional Factors Keep Obama The Favorite

President Obama seems like a near lock for re-election... Or so it would seem given that potential Republican candidates are dropping out of the race quicker than they can say "Reagan".

An often cited reason for Obama's great chances is that first term Presidents for a given party's term (so George H.W. Bush was actually the third term of a Republican administration) almost always win re-election. But is this true? Is another factor helping him?

The best way to understand whether or not Obama is aided by being a first-term President is to model past election results.

Alan Abramowitz's "Time for Change" model attempts to achieve this task. Utilizing second-quarter GDP growth in the Presidential election year, Presidential approval in the second quarter of the election year, and a dummy variable (1 or 0) for whether the party in the White House has completed 1 or more terms, he finds that the term variable is very important.

In fact, President Obama is estimated to garner 4.4% more of the popular vote than he would if his party were in its second term in the White House for a projected percentage between 53-54%.

Abramowitz's model, however, as good as it is at predicting, is not a straight fundamental model. The Presidential approval term can encompass many variables (wartime fatalities for instance) and does not explain the "fundamental" cause of disapproval of the President's job.

To test whether Abramowitz's results on term of the party in the White House hold true in a totally fundamental model, I turn to Douglas Hibbs' well-respected fundamental model based off of 15 elections worth of weighted real disposable income growth per capita (DPI) and fatalities in aggressive foreign wars* over the Presidential term.

We find that the addition of the variable for term of the party controlling the Presidency (0 for 1st, 1 for 2nd or later) does have a statistically significant impact (at the 90% confidence interval) on Hibbs' model. Given the current and projected state of DPI for a weighted value of 1.18 (see this post for more on economic projections), Obama is estimated to receive 51.6% of the two-party vote.

If 2012 was the end of the second or later term of a Democratic administration, Obama's estimated vote percentage would be 49.3%. The effect of the term variable seems less than the Abramowitz model, but enough to turn Obama from an underdog to a favorite.

One other factor that some argue is helping Obama's re-election chances is the Republican House. Regardless of the ideology of this Republican House, the center of the American electorate seems to like divided government.

Plugging an ordinal variable (0 for no, 1 for half, 2 for yes) into our reformed Hibbs' model (with term of the President taken into account), we can reestimate our model to test whether or not Congressional control by the President's party adds to our ability to explain past Presidential election results.

It turns out that when President's party controls Congress, it hurts the incumbent's party chance of re-election to the White House. This effect is statistically significant at the 95% confidence level and makes the term variable have a greater affect and is more significant. This new model has an in-dataset margin of error at 95% confidence of 3.3% and explains 92.9% of the past 15 Presidential elections.

Our re-estimated model controlling for Congress projects Obama to win 51.8% of the two-party vote (little different from 51.6% for the model without a variable for Congressional control).

If, however, the Democrats controlled all of Congress (2 for yes) instead of half of it (1), Obama's predicted percentage would drop to a calculated 50.2%. As the table below illustrates, his projected vote would drop to 46.1% if this control of Congress were combined with a second (or later) White House term.

As it is, Obama looks to be a favorite, but his election is not assured even given his term and split control of Congress. The few Republican challengers left in the race have a decent shot of winning and even better chance if the economy does worse than forecasted.

*The variable takes on a value of 0 in 2012 because the war must be started by the current President's party.

Monday, May 09, 2011


Predicting Elections is like the NFL... We have parity (and may not have a major contest until 2012)

As some of us have tried the first attempts at predicting the 2012 elections, we are all wondering which prediction will be most accurate at the end of the day. Can we skip most of the "expert" predictions and concentrate on only one website. The answer it would seem is yes... but only because we're likely to get the same answer wherever we go. Why?

Pretty much all expert projections are privy to and rely on the same polling data, and most pollsters are as accurate as one another. Nate Silver's pollster rankings suggest that this is not the case, but there is considerable debate within the academic/polling community over whether his rankings are statistically significant in most cases or hold any predictive value for future campaigns.

Without reliving old arguments over statistical significance (see this Mark Blumenthal piece on anti-significance and Silver's response), I think the predictive value is far more important.

Following the 2010 midterm elections, Nate released a preliminary 2010 general election pollster scorecard* for eight pollsters. As you can see, their errors ranged from 3.3-5.8% with Rasmussen registering as the least accurate. How did their relative rankings compare with past performance?

There was actually a slightly insignificant relationship. The highest ranking pollster (Quinnipiac) was actually ranked lowest in the previous incarnation of the pollster rankings. YouGov, which ranked 7th, came in at 3rd. Disturbingly, the prior rankings had punished YouGov because it conducts polls over the Internet. In other words, an effort to add to prior pollster performance to create a more accurate forecast of future accuracy did not help.

Based on this evidence as well as the fact that a different rating system by American Research Group's Dick Bennett that included data from the primary actually found Quinnipiac towards the bottom of the pack (due a poor primary performance), I do not believe that, for the most part, past pollster accuracy foretells future performance.

Not surprisingly then, poll aggregation techniques are as accurate as each other. Chris Bowers (a pioneer of simple polling averages) found that the difference in accuracy between the final predictions of,, and a simple 25-day polling average for the 52 closest Presidential, Senatorial, and Gubernatorial contests in 2008 and early 2010 (before the general) was only 0.27% (with the simple average coming out statistically insignificantly ahead).

In the 2010 general election, Bowers' calculated that in closest 45 campaigns the difference in mean error between,, Real Clear Politics, and a simple 25-day polling average was only 0.31% (with FiveThirtyEight coming out statistically insignificantly ahead). Dick Bennett's review of the aggregation methods found similar insignificance in error.

What about in the House of Representatives, where neither Bowers nor Bennett have roamed?

Few websites, I know of, actually attempt to predict the results (not just the winner) in each House race. To do so, you need not only polling data, but also past district voting history (on both the Congressional and Presidential level) among other variables.

The only two that did so in 2010 were and Stochastic Democracy (which I have previously contributed to). Looking at all the House races that had both a Republican and Democratic candidate (406 in total), I found that average error (on the two-way) was 6.27% for and 6.72% for Stochastic Democracy. This difference is not statistically significant at any mathematically accepted level.

What happens when we just look at who better predicted the winner? had 19 missed calls, while Stochastic Democracy had 18. Again, not statistically significant. Another prominent site, Larry Sabato's Crystal Ball (to whom I have recently contributed) also had 18 missed calls. Most prominent websites had similar track records.

Where does this leave us? Any prognosticator/pollster who claims that they are more accurate than the other guy probably is not (at least for more than one cycle). The fact that a simple 25-day and simple Real Clear Politics average does as well as some of the more complicated methods in statewide contests indicates that those at home can try their own hand at beating the pros (and on any given day have a decent chance of doing so). Most importantly, I feel secure knowing that readers are getting good information no matter where they go.

*I have not seen an updated scorecard, but would be more than happy to update the post based on a new one.

Note: If you are interested in any part(s) of the 2010 House dataset, feel free to email.

Thursday, May 05, 2011


Minnesotan Marriage Ban Is Early Favorite

It now seems likely that Minnesotan voters will vote in 2012 on a constitutional amendment to ban same-sex marriage. If you have been following the national polls and punditry, you might be led to believe that the amendment will probably fail. At this point, however, I would put the money on it to pass. Why?

1. The latest polling (I could find) discovered that more Minnesotans are against same-sex marriage than are for it. The poll from September 2010 found that among likely voters 49% opposed same-sex marriage, while 41% were for legalizing same-sex marriage. Reallocating undecideds based on decided voters (as there is no undecided when it comes time to vote), 54% of Minnesotans are against legalizing same-sex marriage.

Some might point to a 2006 poll, which indicated that even though most Minnesotans were against same-sex marriage, they would vote against a constitutional amendment to ban it. The fact is that polling before the California's infamous Prop. 8, a constitutional ban against gay marriage, polling suggested a similar split*: a number of Californians who were against same-sex marriage would vote against Prop. 8. In the end, most voters against same-sex marriage, but also against the amendment, voted for Prop. 8. I would expect a similar trend in Minnesota.

2. Minnesotan demographics indicate that the amendment is likely to pass. Take a modification of Nate Silver's same-sex marriage model that controls for a state's religiosity, a state's median voter's level of conservatism on social issues (with -2 being very liberal to 2 being very conservative), the year of the election, whether the election was held during an off-year or non-Presidential primary, and whether the ballot measure sought to ban same-sex marriage and civil unions or just same-sex marriage.

64% of Minnesotans consider religion to be an important part of their lives; Minnesotans' tend to be quite moderate on social issues (with a score of -.08); 2012 is 15 years after the first gay marriage amendment nationwide; 2012 is not an off-year; and, the measure seeks only to ban same-sex marriage. Given these variable values, the model projects the marriage amendment to pass with a little over 56% of the vote (quite close to the 54% polling number above).

Ah, but only if it were so easy to predict. Points 1 and 2 come with some caveats that deserve explanation.

1. Like the rest of the nation, support for same-sex marriage legalization seems to be increasing. In the aforementioned 2006 poll, only 29% of Minnesotan voters** supported gay marriage, while 54% opposed. That means that in 4 years, support climbed 12%, while opposition dropped by 5%. If that trend continued over the next 2 years, we'd be looking at an electorate that evenly split on the marriage question come 2012.

2. The demographic model has a within dataset margin of error at 95% of about +/- 8.3%. The model is telling us that it is not unreasonable (even if unlikely) that the Minnesotan same-sex marriage ban fails with 49%. For Maine's 2009 same-sex marriage referendum, the model out-of-dataset forecasted the ban to fail with a little greater than 47% of the vote, but it actually passed with a little less than 53% of the vote (an error of about 5.5%).

Keeping these qualifications in mind, I should drive home the point that past history does not look too kindly upon the pro-same-sex marriage side.

As I had previously found and Patrick Egan has expanded upon, same-sex marriage ballot questions tend, if anything, to do worse on election day than pre-election polls predict. In fact, Egan found the bans ("yes" side) picked up, on average, 7% support from the final polls, while the "no" side picked up no appreciable support. In Minnesota, therefore, we might expect the ban to pass in the high 50's, instead of the 54% projected above.

Further, Egan demonstrated that campaigns have little effect on the outcome. The polls six months before the election occur were about as accurate as those right before the election. While October 2010 is far more than six months out from 2012, I would imagine that the swing in favor of same-sex marriage (and against the ban) will probably not advance to the point that two sides reach equality in vote share as spoken about above.

Given all this information, the ban side seems to have the edge. The election will not take place until 2012 and many things may change. Minnesota may defy the trend, but I would not count on it.


* The two situations are not exactly similar, however. Without the constitutional amendment, California would have continued to allow same-sex marriages. Even if the marriage amendment fails in Minnesota, state law bans same-sex marriage. Perhaps, more of the "no to marriage, but no ban" folks will vote against the amendment in Minnesota.

** The sample population for the two polls are not the same. The 2010 poll employed a likely voter sample, while the 2006 sample utilized a registered voter model. 2010 was a very Republican year, so it is probable that the electorate was more liberal in 2006 and is more liberal in 2012. That makes the gains in support of same-sex marriage between 2006 and 2010 more impressive and means that new polling for 2012 might reveal a closer election than the 2010 poll indicated.

Tuesday, May 03, 2011


Britons should vote NO on AV

On Thursday, Britons will vote on the voting system to be used in future parliamentary elections. This blog does not endorse candidates or parties, but it does endorse methods of voting and vote counting. The current British method, plurality, is elegantly simple: each voter selects one candidate, and the candidate with the most votes wins the election. It is not perfect, but the substitute method up for a vote, alternative vote (or instant runoff voting), is far too flawed for British voters to approve.

Alternative vote (AV) is a type of preferential voting in which voters are asked to rank the candidates from first to last. The basic idea is that if no candidate is the first choice of 50% + 1 voters, then the candidate who received the fewest first place votes is eliminated. This candidate's voters then have their votes reallocated to the candidate they ranked second. This reallocation process continues until one candidate achieves 50% + 1 votes (more on this later). A majority is achieved (or so we think)!

AV supposedly gives voters more freedom of expression to vote for the candidates they want. I will allow AV supporters to develop this argument further.

What I want to do first is give you three reasons why AV is an unacceptable system to me.

1. No-Show Paradox. The number 1 rule I hold for any voting system is that when you vote for a candidate you should be helping her/him. Conversely, when you stay home and do not cast a ballot, you should hurt the candidate you want to win. In plurality voting, these simple (and very logical) rules hold true. In AV, these rules do NOT hold.

Consider, the follow 21 voter and three candidate example borrowed from Warren Smith's Range Voting website (a great site for a more in-depth look at the problem described below).

In this example, the Liberal Democrat candidate has the most votes (8), but it does not hold a majority. The Conservative candidate has the second most first places votes (7). The Labour candidate has the fewest first place votes (6), and its voters have their votes reallocated to their second choice.

With the votes reallocated from those who ranked Labour first, the Conservative candidate has a majority with 13 votes and wins. All seems well... but is it?

What happens if 3 of the voters who ranked the Liberal Democrat first got sick on Election Day and could not make it to the polls? The modified electorate from above would look like this

Now, the Conservative candidate has the most first place votes (7), while the Labour candidate has the second most first place votes (6). The Liberal Democrat is eliminated, and its voters have their votes reallocated to their second choice.

All of a sudden, it is the Labour candidate (with 11 votes) who wins the election. Nothing may seem wrong with that at first glance, but a further examination reveals something is quite wrong here. Three voters who preferred the Labour candidate to the Conservative were only able to get the Labour candidate elected by NOT VOTING! Put another way, the three voters who were sick would have gotten their least favorite candidate elected by voting!

The mere thought of such an event occurring is a deal breaker for me. Another scary statistic is that when the AV and plurality winner differ, the chance of a no-show paradox occurring is about 50%!

2. Non-monotonicity. Related to the no-show paradox are violations of monotonicity. Ranking a candidate (e.g. Liberal Democrat) higher should help, not hurt, her/his chances of winning, while ranking them lower should hurt, not help, their chances of winning. Seems pretty obvious, and we know in plurality voting that voting for a candidate helps them, while not voting for them hurts them. Yet, AV fails this simple test.

Consider, this one example, again from Warren Smith's Range Voting website, with 3 candidates and 17 candidates demonstrating how IRV show this terrible characteristic.

Here, the Labour candidate has the most votes (8), but just misses a majority. The Conservative advances to the second round with 5 votes, and the Liberal Democrat is eliminated with 4 votes. With the votes from those who placed the Liberal Democrat first redistributed, the Conservative comes from behind and wins 9 votes to 8 over the Labour candidate. Seems good that a majority was formed... right?

But look at what happens when two of the voters who ranked the Labour candidate first and Liberal Democrat second decided at the last moment that they preferred the Liberal Democrat to the Labour candidate...

Now, the Conservative is eliminated with only 5 first place votes, while the Liberal Democrat and Labour candidate advance with 6 votes. With the Conservatives votes re-distributed, the Labour candidate has won the election over the Liberal Democrat 11 to 6.

Did you just see what happened? 2 voters who had initially preferred the Labour candidate to the Liberal Democrat were able to secure the election of a Labour candidate by ranking the Liberal Democrat over the Labour candidate!

And yes, it is possible (see Smith's website) to ensure the defeat of a candidate by ranking so-said candidate higher (as opposed to ranking a candidate lower to ensure victory as the above example illustrates). In combination, these two monotonic problems occur no less than in 5% of the time in 3 candidate elections. The percentage is even higher for elections with more candidates.

3. AV violates one-man/one-vote. Certain electoral systems (e.g. cumulative voting) allow voters to vote for more than one candidate, but they give each voter the right (even if they choose not to execute it) to theoretically cast and have the same amount of votes counted as one another. The current British system is one-man/one-vote. AV, on the other hand, gives certain voters more votes than others.

Take a gander at any of the examples above. You'll note that the voters who have their first choice eliminated in the first round have their second-choice votes counted in a second round. In other words, they have 2 votes counted. The voters whose top choices make it into the final 2 only have 1 vote counted. If there were more candidates in this election, there is the obvious possibility of some people having infinite votes counted, while others still having only 1.

Now, for those whose first choice is the winner, I have little sympathy. But re-examine our first example,

As shown above, the Conservative wins, while the Liberal Democrat (who would win a plurality election) advances to the second round and loses. The voters who ranked the Liberal Democrat first only have 1 vote counted. This characteristic of AV is even more ridiculous when you realize that the Liberal Democrat voters in this election would have preferred any candidates besides the Conservative. In fact, they could have formed a majority with first-place Labour voters to allow the Labour candidate (Liberal Democrat voters second choice) to win the seat.

An unfair outcome has clearly occurred.

Finally, I want to make two points with regards to the idea that AV allows a majority to be formed.

1. You might be lead to believe that AV guarantees that the Condorcet winner (the candidate who would win one-on-one match-ups against each other candidate), if it exists, wins the election. The truth is that it does not.

Look directly above to the prior example, and you'll quickly realize that if there were one-on-one match-ups, the Labour candidate would win every single one. 14 voters prefer the Labour candidate to the Conservative, and 13 voters prefer the Labour candidate to the Liberal Democrat. Yet, in AV, the Labour candidate is the first one eliminated. AV does not even do something that many would argue it should.

2. Recognize that the candidate who eventually wins the majority does not necessarily have the vote of 50% + 1 of the voters who cast a ballot. When a ballot is filled with many candidates, many people might not rank all of the candidates (e.g. for lack of time).

I can speak from real experience. In the 2010 Dartmouth Student Assembly Vice-Presidential election, which utilized AV, Brandon Aiono won by 7 votes over Will Hix (1,075 to 1,068). It turns out, however, that 2,246 ballots were cast in this race. That means that Aiono actually only won with a little less than 47.9% of the people who voted in this race.

If AV actually encourages more third-party voting (which is debatable) as some AV supporters suggest, then it really is possible than many Britons will not rank every candidate. If they do not rank every candidate, then we could get a winner who does not have support from 50% + 1 of the voters.

This last example is typical of AV's failure to deliver. AV gives voters a false sense of security that they are in greater control of the electoral process. In reality, they are in less control and cannot truly be sure what their vote truly means.

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