I risultati delle elezioni parlamentari italiane del 2006 erano così incerti che nessun sondaggio pre-elettorale avrebbe potuto prevderli con precisione. In un lavoro precedente degli stessi autori, l'uso di un indice di capacità predittività - l'A di Martin e collaboratori - in relazione ai sondaggi pre-elettorali del 2001 e del 2006 aveva mostrato che questi avevano avuto prestazioni deludenti e sovrastimato i consensi per le coalizioni vincenti. In questo nuovo lavoro gli stessi autori prendono in esame i sondaggi pre-elettorali riferiti alle elezioni politiche del 2008. Nonostante diversi fattori che avrebbero potuto inficiare la capacità predittiva dei sondaggi - fra cui labrevità della campagna elettorale, una significativa ristrutturazione delle coalizioni elettorali, una diversa rilevanza dei partiti minori esclusi dalle maggiori coalizioni, l'ulteriore crescita della quota di famiglie non dodtate di utenze telefoniche di rete fissa e l'accresciuto astensionismo -- e a dispetto dell'aggravamento di alcuni problemi metodologici attinenti ai sondaggi medesimi, la capacità predittiva è migliorata rispetto al 2001 e al 2006, Inoltre, gli autori propongono un uso innovativo di A, per valutare le prestazioni dei sondaggi in merito all'allocazione dei voti *entro* le coalizioni di centro-destra e di centro-sinistra.
Two years have passed since the last Italian parliamentary elections, the results of which were so close that no pre-election poll could have reliably predicted the winner. In preceding work by the two authors, a measure of predictive accuracy - Martin et al.'s A - was applied to the 2006 and 2001 Italian general elections and showed that in both instances published polls performed badly and overestimated voters' support for the winning coalition. In this new article, the authors monitor the performance of published polls conducted during the 2008 election campaign. The polls' predictive accuracy could have been further impaired, with respect to the past, by several factors: the relative brevity of the campaign; a comprehensive re-structuring of electoral alliances; the ensuing need for voters to adapt to the new scenario; the renewed relevance of smaller parties excluded from the major electoral alliances, thereby weakening the election's "bipolar" structure; an increasing telephoneinterviewing coverage error due to the high incidence of households having only mobile phones or no phone; decreasing voter turnout. Despite these potential problems and published surveys' several methodological shortcomings, predictive accuracy improved with respect to 2001 and 2006. The authors also use A in an innovative way, i.e., to assess polls performance regarding the allocation of votes within the centre-left and the centre-right coalitions.
Gasperoni G., Callegaro M. (2008). Un miglioramento immeritato? La capacità predittiva dei sondaggi preelettorali e le elezioni del 2008. POLIS, 22(3), 483-504 [10.1424/28286].
Un miglioramento immeritato? La capacità predittiva dei sondaggi preelettorali e le elezioni del 2008
GASPERONI, Giancarlo;
2008
Abstract
Two years have passed since the last Italian parliamentary elections, the results of which were so close that no pre-election poll could have reliably predicted the winner. In preceding work by the two authors, a measure of predictive accuracy - Martin et al.'s A - was applied to the 2006 and 2001 Italian general elections and showed that in both instances published polls performed badly and overestimated voters' support for the winning coalition. In this new article, the authors monitor the performance of published polls conducted during the 2008 election campaign. The polls' predictive accuracy could have been further impaired, with respect to the past, by several factors: the relative brevity of the campaign; a comprehensive re-structuring of electoral alliances; the ensuing need for voters to adapt to the new scenario; the renewed relevance of smaller parties excluded from the major electoral alliances, thereby weakening the election's "bipolar" structure; an increasing telephoneinterviewing coverage error due to the high incidence of households having only mobile phones or no phone; decreasing voter turnout. Despite these potential problems and published surveys' several methodological shortcomings, predictive accuracy improved with respect to 2001 and 2006. The authors also use A in an innovative way, i.e., to assess polls performance regarding the allocation of votes within the centre-left and the centre-right coalitions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.