Poll of polls - June 20

on Jun 20, 2012

Time for another update of my poll of polls. With less than two weeks remaining until voting day the race is on! I mean the race for second place because Enrique Peña Nieto of the Partido Revolucionario Institucional has pretty much cinched the presidency for the next six years.

I've now switched to a Bayesian method of pooling the polls. I'm using a Kalman Filter that corrects for House Effects (the bias of each polling firm) as described in Pooling the Polls Over an Election Campaign (pdf), by Simon Jackman. I'm using diffuse priors for the house effects but I could probably switch to using the posteriors for each polling firm from the 2006 election, if I ever get around to modeling it.

The thing that worries the most is that polling firms tend to be highly variable, for example, in 2006 the most accurate pollsters were Reforma and GEA-ISA, but in the last elections they did not perform so well. Oh well, we'll see what happens.

To recap from previous blogs
  • My data comes from the poll of polls by ADN Político.
  • I added a couple of polls conducted by Indemerc and corrected some missing polls from El Universal - Buendía y Laredo
  • I'm using weekly averages of the GEA-ISA daily tracking poll because it has some weird periodical artifacts

References

Pooling the Polls Over an Election Campaign, Australian Journal of Political Science, 2005 V40(4):499-517

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2 comments:

Diego said...

I have some questions. First, Could you find a complete methodology of all polls? I haven't been able to find any social and demographic statistics. The latter makes me think that because we do not know if social and demographic characteristics of the sample are the same for every poll, results won't be pretty accurate and could actually have bias. Moreover, their sample is so small and at the district level it is not significant, doing interviews to 4 people in average by district. It´s interesting you are using the kalman filter to get the unobserved components, I liked it. I appreciate your response.

Diego Valle-Jones said...

Most polling firms keep their methodology secret.

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Thank you for your interesting and insightful comments. I truly look forward to reading them.