Tuesday, December 27, 2011

 

Expecting an Iowa Polling Shock? Don't Be Prepared to Drop Your Jaw

It has become popular to say that the Iowa caucus is where pollsters' dreams go to die. Experts from Mark Blumenthal to Nate Silver have noted that Iowa caucus polling accuracy is less than ideal (and certainly less than in other contests)... But I dare say that our inability to predict the caucuses is somewhat overblown?

First, let's remember that the Republican Iowa caucus is not actually a caucus. It's a straw poll. The difference? In a caucus (as the Democrats have in Iowa), voters have to gather for hours on end openly declaring their support for a candidate.

In a straw poll, voters merely have to listen to a few speeches and then cast their votes on secret ballots. This makes the act of voting far easier and invites less peer pressure to vote for a specific candidate (i.e. having a voter change their mind to fit what their neighbors are doing).

Another distinction is that in the Democratic caucus voting thresholds exist. Candidates who do not meet this threshold (15%) have their voters reallocate their votes to other candidates. On the Republican side, voters vote once and that's it. No thresholds.

Both of these facts make polling a Republican contest easier in theory than a Democratic contest.

What about the rather convincing charts indicating relatively high pollster error for past Republican contests in Iowa?

The truth is that we are dealing with a lot of old data. Note that with the exception of 2008, all the Iowa Republican caucus polling data is from 2000 and before. Why is that important?

It turns that polling data has gotten incredibly more accurate since 2000. For instance, you may remember that the final polls in 2000 incorrectly indicated that George W. Bush would win a small but solid victory in the popular vote over Al Gore. What you may not remember is that despite being relatively inaccurate, polling in 2000 was better than in all but two presidential elections since 1960.

Polling in 2004 and 2008, on the other hand, came with decimal points of correctly projecting the presidential popular vote. Polling for state contests has similarly become consistently more accurate in the 2000's.

Despite all the problems with new untested pollsters with supposedly unreliable techniques, polling in 2010 was on-par with other midterm elections since 2002. In 2011, we had automated pollsters (who are missing the cellphone population and have terrible response rates) correctly forecasting upsets in special Congressional elections (see New York 9 and 26).

Fitting with this pattern, the 2008 Republican Iowa caucus was more accurately polled than any before it. The average difference between the final polling average and candidates' actual percentage was only 2.7%. The biggest difference in percentage, 5%, was far less than the biggest difference in previous years.

If the trends of accuracy continue, polling in 2012 in both the Iowa caucus and other contests is more likely to be like 2008 than any other year.

None of this is to say that we will not see a "surprise" in Iowa. Considering how tightly the candidates are clustered, a 5% error between the polls and actual margin could make all the difference in the final outcome and, more importantly, media spin. That said, the polls are more likely to get a lot more right than wrong.

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