Important
Ireland Votes methodology is periodically reviewed and may evolve over time as new electoral, constituency and polling data becomes available.
1. Notional Changes
For some elections, direct comparisons with previous results can become misleading because constituency boundaries or seat allocations changed between elections. Ireland Votes thus produces
notional estimates to create a more meaningful baseline for comparison.
“If the previous election had been fought under the revised electoral arrangements, what would the likely result have been?”
These figures are analytical estimates rather than official historical results. For the official result of a previous election, where available, you can view the results of that election on irelandvotes.com.
Where constituency boundaries have been redrawn
Where constituency boundaries change, Ireland Votes estimates how votes from previous elections would likely have translated into the revised constituency map.
Areas transferred between constituencies are identified and mapped to their historical electoral geography where possible. Past voting patterns are then redistributed into the new constituency structure.
Using these estimates, the previous election is effectively re-run under the revised map and seat totals to generate a projected notional outcome.
As revised constituencies can combine areas with differing political characteristics, these estimates should be viewed as informed approximations rather than exact reconstructions.
Where boundaries remain unchanged but seat totals change
In some elections, constituency boundaries remain identical while the number of representatives elected changes.
One example is the 2017 Northern Ireland Assembly election, where constituencies remained geographically unchanged but moved from electing six members to five.
In these situations, Ireland Votes retains the original vote totals but re-runs the election using the revised seat allocation.
For Single Transferable Vote elections, quota and seat totals are recalculated before estimating how candidates and parties would likely have performed under the revised structure.
This creates a baseline reflecting the electoral conditions actually used at the subsequent election.
2. The Ireland Votes Aggregate
The Ireland Votes Aggregate is a rolling polling model designed to estimate the underlying level of support for political parties and electoral blocs at a given point in time.
Individual polls provide snapshots of opinion, but each survey contains unavoidable statistical noise arising from sampling variation, fieldwork timing, methodology and random error. As a result, individual polls can occasionally overstate or understate underlying support. Thus, rather than treating any one survey as determinative, the aggregate combines multiple publicly available polls to identify the broader signal within the polling environment.
Polls enter the model on a rolling basis, with observations weighted according to recency. More recent fieldwork carries greater influence than older surveys, allowing the aggregate to respond to genuine shifts in public opinion while reducing the effect of temporary volatility.
The model is designed to smooth short-term fluctuations and limit the influence of isolated outlier polls which may arise through sampling variation or methodological effects. This produces a more stable estimate of trend movement over time.
No explicit turnout assumptions, constituency-level modelling or seat projections are incorporated into the aggregate itself. Its purpose is to estimate current vote intention rather than forecast electoral outcomes.
As new polling becomes available, historical estimates may adjust modestly as additional information enters the rolling series.
