Comparing Strategies for Estimating Constituency Opinion from National Survey Samples

Political scientists interested in estimating how public opinion varies by constituency have developed several strategies for supplementing limited constituency survey data with additional sources of information. We present two evaluation studies in the previously unexamined context of British constituency-level opinion: an external validation study of party vote share in the 2010 general election and a cross-validation of opinion toward the European Union. We find that most of the gains over direct estimation come from the inclusion of constituency-level predictors, which are also the easiest source of additional information to incorporate. Individual-level predictors combined with post-stratification particularly improve estimates from unrepresentative samples, and geographic local smoothing can compensate for weak constituency-level predictors. We argue that these findings are likely to be representative of applications of these methods where the number of constituencies is large

Tories still short of a majority: Hix-Vivyan prediction up to 26 April

We have updated our election prediction model, based on national voting intention results from all polls with fieldwork up to and including 26 April

If not polls, then betting markets?

In this post, Chris Hanretty, Ben Lauderdale and Nick Vivyan investigate the predictive performance of the betting markets relative to their electionforecast.co.uk forecasting model

The Misreporting Trade-off Between List Experiments and Direct Questions in Practice: Partition Validation Evidence from Two Countries

To reduce strategic misreporting on sensitive topics, survey researchers increasingly use list experiments rather than direct questions. However, the complexity of list experiments may increase non-strategic misreporting. We provide the first empirical assessment of this trade-off between strategic and non-strategic misreporting. We field list experiments on election turnout in two different countries, collecting measures of respondents' true turnout. We detail and apply a partition validation method which uses true scores to distinguish true and false positives and negatives for list experiments, thus allowing detection of non-strategic reporting errors. For both list experiments, partition validation reveals non-strategic misreporting that is: undetected by standard diagnostics or validation; greater than assumed in extant simulation studies; and severe enough that direct turnout questions subject to strategic misreporting exhibit lower overall reporting error. We discuss how our results can inform the choice between list experiment and direct question for other topics and survey contexts

Comparing Strategies for Estimating Constituency Opinion from National Survey Samples

Political scientists interested in estimating how public opinion varies by constituency have developed several strategies for supplementing limited constituency survey data with additional sources of information. We present two evaluation studies in the previously unexamined context of British constituency-level opinion: an external validation study of party vote share in the 2010 general election and a cross-validation of opinion toward the European Union. We find that most of the gains over direct estimation come from the inclusion of constituency-level predictors, which are also the easiest source of additional information to incorporate. Individual-level predictors combined with post-stratification particularly improve estimates from unrepresentative samples, and geographic local smoothing can compensate for weak constituency-level predictors. We argue that these findings are likely to be representative of applications of these methods where the number of constituencies is large

Combining national and constituency polling for forecasting

We describe a method for forecasting British general elections by combining national and constituency polling. We reconcile national and constituency estimates through a new swing model

Decomposing Public Opinion Variation into Ideology, Idiosyncrasy, and Instability

We propose a method for decomposing variation in the issue preferences that US citizens express on surveys into three sources of variability that correspond to major threads in public opinion research. We find that, averaging across a set of high-profile US political issues, a single ideological dimension accounts for about 1/7 of opinion variation, individuals’ idiosyncratic preferences account for about 3/7, and response instability for the remaining 3/7. These shares vary substantially across issue types, and the average share attributable to ideology doubles when a second ideological dimension is permitted. We also find that (unidimensional) ideology accounts for almost twice as much response variation (and response instability is substantially lower) among respondents with high, rather than low, political knowledge. Our estimation strategy is based on an ordinal probit model with random effects and is applicable to other data sets that include repeated measurements of ordinal issue position data

Four electoral records that might be broken in May

Many observers have suggested that increasing fragmentation of the popular vote could lead to electoral outcomes that break with UK electoral history, but what is the probability that the 2015 election really will be exceptional? In this post, the team from electionforecast.co.uk discuss four electoral records that might be broken in May

What would the election look like under PR?

The further fragmentation of the UK’s party system in 2015 is likely to lead to the most disproportionate outcome of any election in the post-war era. In this post, Jack Blumenau and Simon Hix, along with the team from electionforecast.co.uk, ask what the House of Commons might look like if the election were held under a more proportionate voting system. If members were elected from small multi-member constituencies, the main beneficiaries would be the Liberal Democrats and UKIP, while the main losers would be Labour, the Conservatives and the SNP

Predicting the polls – April

Each month, the team from electionforecast.co.uk compare new constituency polls as they are released to their estimates of what polls would show in those constituencies. This allows for an assessment of the accuracy of their modeling approach. More information about the overall model can be found here. The results presented in this post use all constituency polls released by Lord Ashcroft in April so far