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538: Pollster House Effect, State Home Court Advantage, Jobs Report correlates

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mshan

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Nov 16, 2004
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Decided to put together a few links I've read from 538 website on how they recommend interpreting polls:

Pollster House Effect:



http://fivethirtyeight.blogs.nytimes.com/2012/06/22/calculating-house-effects-of-polling-firms/






State Home Court Advantage:


"Although this calculation might seem involved, the way to read the voting index is relatively straightforward. In Missouri, for example, the index is Republican plus 6.7 points. What this means is that if the popular vote were exactly tied nationally, we’d expect the Republican candidate to carry Missouri by 6.7 percentage points."
http://fivethirtyeight.blogs.nytimes.com/2012/07/24/state-and-national-polls-tell-different-tales-about-state-of-campaign/







Historical Monthly Jobs Report correlations:



http://fivethirtyeight.blogs.nytimes.com/2012/05/04/has-obamas-magic-jobs-number-changed/

Caveats:
- Skewed seasonal adjustment factor?: http://ftalphaville.ft.com/blog/2012/07/06/1074731/seasonality-and-jobs-one-more-time/
- Unemployment rate by Education Attained: http://www.bls.gov/web/empsit/cpseea05.htm
- Unemployment rate by Race / Sex: http://www.bls.gov/cps/cpsaat07.htm
- Most true swing states, except Florida and Nevada I believe, have unemployment rates well below national average and IIRC Nevada's rate is falling fast, though it started from very high level
- Morningstar economist Bob Johnson says seasonally adjusted monthly jobs gains have been about 150K on average for first 6 months. He sees modest acceleration of economy in second half and monthly jobs gains accelerating in particular because of new home starts tailwind (construction workers getting hired. e. g. IIRC, Toll Brothers recently said they are seeing shortage of construction workers in some markets, and they see strength in all markets across country they serve. I forgot exact number, but I think he said around 175K per month was his guess) http://www.morningstar.com/cover/videocenter.aspx?id=563032







Disingenuous Outliers?:


"Perhaps 90 or 95 percent of the time, taking a simple average of the polls will work just about as well as the more complicated FiveThirtyEight method. But this is rare instance where taking all the polls at face value may be a mistake, and the additional checks-and-balances the FiveThirtyEight method applies are worth the trouble."
http://fivethirtyeight.blogs.nytimes.com/2012/08/28/aug-27-michigan-isnt-a-tossup/







Seven Ways to Read a Poll:

http://fivethirtyeight.blogs.nytimes.com/2012/08/24/aug-23-seven-ways-to-evaluate-a-poll/
"Any time that a candidate is leading in a state, and he simply maintains that lead, that counts as a modest positive for him because time is running off his opponent’s clock. A three-point deficit in April is very easy to overcome. In August? Still plenty of time, but there’s room for a touch of concern. On election eve? Oops — it’s probably too late.

There’s no need for Mr. Romney to panic yet, especially since he has gotten his share of decent state polls recently. But if Mr. Obama still holds a three-point lead in Ohio after the party conventions, it’s going to qualify as a negative for Mr. Romney every time that he fails to reduce the gap."
 
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PokerGuy

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Jul 2, 2005
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Good info, thanks for the links, I'll check it out some more later this evening. :thumbsup:
 

Farang

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Jul 7, 2003
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He is pretty dismissive of Michigan, and makes a good point on two of the firms, but I'm going to withhold judgment that things haven't tightened until we get more recent results from the national firms. What's to say the difference in numbers isn't simply the difference between July and August?

I'm also curious why we haven't got a South Carolina poll. Everything we've seen indicates a possibly tight race. Though I doubt it, we get polls from Oklahoma and Texas so why not?
 

mshan

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"It is hard to conceive of Mr. Romney winning the election but losing Florida because Florida is an ever-so-slightly Republican-leaning state. If he loses it, he’s probably having trouble elsewhere on the map as well. It’s quite unlikely that Mr. Romney loses Florida but wins a state like Michigan or Pennsylvania, for instance.

Still, the state is idiosyncratic enough that it could behave differently, moving in one direction while the other swing states move in another. Each party begins with some strengths and weaknesses in the state, and regions that are vital to its path to victory there."
http://fivethirtyeight.blogs.nytimes.com/2012/08/29/in-florida-tampa-is-essential-to-romney-election-hopes/?gwh=C0AF4730083CEE9421F6A4DF73B93EB8





Another interesting comment I heard this morning (I think it was Chuck Todd or David Gregory) was that election is not just down to handful of swing states, but 17 media markets in total across whole country.

Columbus, OH ( http://www.thelantern.com/campus/obama-reiterates-importance-of-youth-vote-hints-ohio-state-return-1.2888194#.UD4qTY5k0QI) and Richmond, VA metro were previously mentioned on PBS Washington Week in past. And someone else recently mentioned Miami metro as also possibly pivotal if election truly tightened up to dead heat in popular vote on election day.
 
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mshan

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Nowcast vs. Nov. 6 projection:



"But what about this year? The national polls have been exceptionally stable, dating back to late 2011. Except for a period in February and March when Mr. Romney was struggling in the Republican primaries, they’ve pretty much always showed something on the order of a two-point lead for Mr. Obama.

In fact, as measured by the standard deviation of national polls since November, this has been the least volatile polling year ever. The standard deviation in the national polls has been 3.7 percentage points, as compared with a historical average of 6.7 points.

What this means is that we should probably expect fairly small convention bounces. The polls have remained quite steady through events like the Supreme Court’s ruling on Mr. Obama’s health care bill, various discouraging and encouraging economic reports, and Mr. Romney’s selection of Representative Paul. D. Ryan of Wisconsin as his running mate. The conventions will probably produce some effect, but it would be an upset if it were all that dramatic given how immovable the polls have been so far.

Specifically, the benchmark is for a convention bounce of about four points for each candidate. Since Mr. Romney trails Mr. Obama by about two percentage points now, this implies that he’d move ahead of him by about two percentage points instead in polls conducted immediately after this week’s convention in Tampa, Fla.

If Mr. Romney gets a larger bounce than that — say, pulling ahead of Mr. Obama by perhaps four to six points in the national polls — that would be a bullish sign for him. This wouldn’t reflect all that large a bounce as compared with the historical average. However, it would be pretty impressive given how hard it has been for the candidates to move the numbers for any reason at all this year.

By contrast, if Mr. Romney only pulls into a tie with Mr. Obama, or still trails him in polls conducted this weekend, that would be a troubling sign for his campaign. The track record of challengers who failed to lead after their conventions is not good."

"Adjusting for the Convention Bounce


As I mentioned, the FiveThirtyEight forecast will adjust for the convention bounces.

Mathematically, this adjustment is not complicated: we’ll just subtract out the projected effects of the convention from the polls.

So, for example, if Mr. Romney holds a five-point lead in a poll conducted this weekend, the model will instead treat that as a one-point lead. This is because this should be right in the midst of his convention bounce and because our benchmark for his convention bounce is four points this year.

This also implies that if Mr. Romney does not gain any ground in the polls after this convention, the model will treat that as a significantly negative factor for him. Then Mr. Romney will have to hope that Mr. Obama does not get any convention bounce either.

I know that some readers will not like the convention bounce adjustment. But it’s critical to remember that a convention bounce is almost always temporary. Sometimes, the bounce will be large enough that a candidate will go from a losing position to a winning one even after it fades, as Mr. Clinton did in 1992. But the polls almost always overrate a candidate’s standing in the interim.

We do hedge against the convention bounce adjustment in two ways, however. First, in addition to adjusting the polls during the convention period, we’ll also assign them less weight. (Specifically, polls conducted when the absolute value of the convention bounce is at its highest will receive a 50 percent penalty, with everything else scaled accordingly.)

More important, we have an alternative for those of you who prefer to look at the polls on an “as-is” basis. That is what we call our “now-cast,” which is our estimate of what would happen if the election were held today. We give the now-cast less emphasis than our forecast, but you can find it by clicking the “now-cast” tab in the right-hand column of this page.

The now-cast will not apply the convention bounce adjustment. It’s possible that one of the candidates could pull ahead in the now-cast while losing ground in the forecast, if he gets some sort of a convention bounce, but it’s a below-average one.

The now-cast also differs from the forecast in other ways. It does not include any economic variables, as the forecast does. It weights the most recent polls somewhat more heavily. And it has a smaller margin of error associated with it, because there is less uncertainty about what would happen in an election held today than the one that will take place in November. But it should give you more options for how you evaluate our data.

Still, the forecast is our signature product. We expect the convention bounces to be small this year. But if Mr. Romney gets no convention bounce at all, or a bounce of only one or two percentage points, it will be appropriate to take a more pessimistic view of his chances of winning in November."









http://fivethirtyeight.blogs.nytimes.com/2012/08/29/measuring-a-convention-bounce/
 
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mshan

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538 forecast model's economic inputs:

"The most significant change to our presidential forecast model this year is that it contains an economic index, which is used to guide forecasts along with the polls.

In fact, as you may have seen since we began our short daily summaries of the model’s output, new economic data often has just as much influence over the forecast as the latest poll from Ohio or Florida.

I have some fairly strong views about the right way to use economic data in a forecasting model like this one. This is fundamentally a very challenging problem because there have been only 16 presidential elections since World War II, and yet there are dozens and dozens of plausible economic variables to pick from. (The Federal Reserve’s Web site, in fact, now publishes about 45,000 economic statistics.)

The historical evidence is robust enough to say that economic performance almost certainly matters at least somewhat, and that poorer economic performance tends to hurt the incumbent party’s presidential candidate. Likewise, it seems clear that the trend in performance matters more than the absolute level — otherwise, Franklin D. Roosevelt would not have been re-elected easily with an unemployment rate well into the double digits (although rapidly declining) in 1936.

But we just do not have anywhere near enough to data to make confident claims about exactly which economic variables are important. For that matter, most of the more obvious choices for economic variables have performed about as well as one another on the historical data anyway. Each one gets some elections right and some wrong.

Let me explain some of the choices I made about the model in light of this problem."



http://fivethirtyeight.blogs.nytimes.com/2012/07/05/measuring-the-effect-of-the-economy-on-elections/




And here's alternative to Nate's take who apparently was just as accurate at calling elections in 2008: http://election.princeton.edu/faq/

(apparently doesn't use any economic variables; also says to wait till end of September to charts more accurately, and specifically said to ignore polls for about 3 weeks after conventions to get better read of state of race)
 
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mshan

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"North Carolina had been reliably Republican for more than two decades. Even Bill Clinton, a Southerner who managed to carry other Southern states, fell short in North Carolina. But over the past few decades, the state’s economy has become much more diversified, remaking the state’s political landscape.

Longtime economic engines in the state, like tobacco, textiles and furniture, have been fading, while newer sectors — like banking, biotechnology, pharmaceuticals and telecommunications — have been growing. New kinds of jobs have attracted new kinds of voters, and North Carolina is younger, more diverse and better educated than it used to be.

But Mr. Obama’s 2008 victory in North Carolina came early. Favorable political conditions nationally and a substantial surge in turnout pulled the state into the Democratic column ahead of schedule. North Carolina, while more competitive than it used to be, is still to the right of the national tipping point, and Mitt Romney has had a slim lead in most surveys of the state conducted this year."
http://fivethirtyeight.blogs.nytimes.com/2012/09/04/in-north-carolina-obamas-2008-victory-was-ahead-of-schedule/
 
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