There are a lot of reasons why would not want to use acces panels for predicting electoral outcomes . These are well discussed in many places on- and offline. I’ll shortly summarize them, before adding some thoughts to why access panels do so badly predicting election outcomes.
1. Access panels don’t draw random samples, but rely on self-selected samples. A slightly better way to get panel respondents is a quota sample, but even these have problems, well discussed here, here and here for example.
The night after the election, one can conclude that all pollsters in the Netherlands did a bad job of predicting the election results. All polls were at least off by 20 seats (out of 150), and I expect the newspapers to make headlines of this in the next days. See the table below for the final predictions (before election day), the exit poll and final election results. The last row shows how much each poll was off (in the number of seats
**Poll volatility **
Below, you find the summed changes in parliamentary seats over all parties in consecutive opinion polls for the four main polling firms in the Netherlands in the lead up to the 2012 elections. I will update the table below in the next weeks.
This overview follows from my earlier post on Dependent Interviewing. Maurice de Hond (peil.nl) is the only survey pre-loading earlier voter preferences into survey questions.
In late august of 2011 I attended the Internet Survey Methodology Workshop. There were people from academia, official statistics and market research agencies there. One of the issues discussed there has had me thinking since: the topic of panel conditioning. Some people seem really worried that respondents in panel surveys start behaving or thinking differently because of repeated participation in a survey.
Panel conditioning is closely linked with the issue of ‘professional’ respondents.
Before people believe I’m old-fashioned, I do think that Internet-surveys, even panel surveys are the future of survey research. John Krosnick makes some good points in a video shot by the people from www.pollster.com
Opinion pollers do a lousy job of predicting elections. For a good read, see for example the prediction of the New Hampshere primary in 2008, when all polls predicted Obama to win, but it was Clinton who won (albeit by a slim margin).
In the Dutch context, there are three main polling firms, that each do equally well (or badly). Out of a hundred and fifty parliamentary seats, peil.nl mispredicted 20, while TNS-NIPO and Synovate shared the honor of only missing the target by 16 seats in the 2010 parliamentary election.