Wales Polling Error Analysis
This analysis runs 1000 simulations of the Welsh Senedd election using randomised vote shares within the margin of error of current polling. It applies a further layer of variation by tweaking each party's swing in each constituency based on local factors including region (North/South), porportion of Welsh speakers, income level, urban/rural, etc.
Results are based on latest polling and are updated regularly.
The aim is to show the uncertainty inherent in election projections and how even small errors and regional factors can lead to significantly different outcomes. In many cases the difference between an excellent year for a party and a terrible year is well within a normal polling error.
Political Spectrum Distribution
Distribution of seats across the political spectrum in 1000 simulations. Left includes Labour, Plaid Cymru, Liberal Democrats, and Greens. Right includes Conservatives and Reform.
Constitutional Preference Distribution
Distribution of seats by constitutional preference in 1000 simulations. Pro Indy includes Plaid Cymru and Greens. Unionist includes Labour, Conservatives, Liberal Democrats, and Reform.
Seat Distribution by Party
The following charts show the distribution of outcomes for each party across all 1000 simulations. Taller peaks indicate more likely outcomes while 'tails' indicate extreme outcomes which would require large polling errors. The dashed line shows the Nowcast prediction for comparison.
Hover over the points to see how many times each occurred out of the 1000 simulations. There tends to be less variation amongst very small parties as there are fewer places in which they have a reasonable chance of winning a seat.
Having a tall but narrow disritubution means that a party has several solid seats which are very safe but weaker elsewhere. This can prevent them from falling too far but also means that growth is difficult.
A shorter, broader distribution means that a party has a mix of seats which are safe, at risk, and in with a chance of gaining. This can allow for growth but also puts them at risk of collapse.
Reform
Plaid Cymru
Labour
Conservatives
Liberal Democrats
Greens
Other
Seat Probabilities
Each square represents a seat, and is ordered by that party's likelihood of winning it. Darker squares indicate safer seats, medium coloured squares indicate battleground seats, whilst very light coloured seats would require a big polling miss for that party to win.
Hover over a square for details.
Reform50 potential seats
Plaid Cymru43 potential seats
Labour31 potential seats
Conservatives19 potential seats
Liberal Democrats12 potential seats
Greens10 potential seats
The margin of error uses a normal distribution of polling errors which means that parties are just as likely to over and underperform their Nowcast. The vast majority of misses will have each party's vote share within 2% of the Nowcast but there will be some rare instances where the misses are much larger. As a rule, the bigger the miss, the less likely it is to occur. This means that most results stay close to current polling averages, but occasional larger deviations are possible. This analysis will be regularly updated as new polls arrive.