Monday, January 26, 2004

What Do Early Polls Mean?
A new Newsweek poll shows Kerry leading Bush, 49-46. This is interesting, but could it be too early to tell?

I looked at polling data leading up to the 1996 and 2000 presidential elections. I would like to look at more, but old data is harder to get. I looked at polls from a year prior to the election, to just days before the election. The question is, how far out are the polls accurate?

I looked at the percent of the two-party vote that the candidates got and compared this to the CNN/Time polling data. I figured that if the polls were within 3% (which gives them a 6 point window) I would give them credit for getting it right. However, if they got the results correct nine months out, and then missed it for the next eight polls, I figured that they just got lucky once, and I am not really willing to give much credit for that. Obviously, one could check additional polling groups for their accuracy, but there is a limit to my obsession here.

In 1996, Clinton and Dole split the two-party vote 54-46%. CNN actually, got Dole within 43-49% in Aug, 95, Jan 96, and Mar 96, but then they overestimated Clinton for the rest of the year. On October 15, they gave Dole 43%, which is low, but close. However, on November 3, they dropped Dole back to 41%, so they were wrong even right before the election.

In 2000, Bush and Gore split the two-party vote 49.7% to 50.3%. CNN generally had Bush way too high, including 59% in July 2000. They got close on Sep 8 and Oct 6, but by Oct 27, they had Bush back to 53.3%. So, once again, CNN was off immediately before the election. Therefore, I conclude that presidential polls in January 2004 are for fun only.

While CNN's polls were off, if does not mean they were inaccurate. It could just mean that voter opinion is very fluid. Here is a brief article that says that final polls in 1996 ranged from Clinton by 7 to Clinton by 18. The actual was 8%. This paper on election projections says that polls are pretty accurate up to 90 days before the election, but not longer than that. So I guess we have to wait another 8 months before we can take these polls seriously.

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