Pre-Election Polls in Portugal: Accuracy, Bias, and Sources of Error, 1991-2004

This article examines the performance of the pre-election pollsin Portugal since 1991 and attempts to determine some of thecommon causes of poll inaccuracy in both National Assembly andEuropean Parliament elections. The analysis of poll resultsin this period reveals marked improvements in poll accuracysince 1991, which have brought it to levels that, today, arecomparable to those found in nations where the practice of bothsurvey research and opinion polling is longer and more established.No evidence of a systematic bias against any of the major partiesis found, and sources of error are congruent with those foundelsewhere. However, large errors remain the norm in polls pertainingto European Parliament elections, suggesting a shared inabilityof Portuguese polling organizations in dealing appropriatelywith the problems caused by low turnout and ‘landslide’elections.