Methodology & Attribution

National Projections

1. Collect all available polls with national vote intention for Scottish Parliamentary Constituencies (SPC) and Scottish Regional Constituencies (SRC). Ipsos and Survation regional breakdowns are also collected for regional modelling.
2. Weight by recency (exponential decay, 14-day half-life) so recent polls carry more weight, and by sample size.
3. Remove pollster house effects by measuring each pollster's consistent deviation from the cross-pollster mean — a quantitative correction rather than excluding pollsters entirely.
4. Calculate house-effect-corrected national polling averages.

Regional Projections

1. Start with 2021 baselines, mapped to new 2026 boundaries.
2. Apply proportional swing to regions based on the national polls.
3. Combine with regional polls from Ipsos and Survation — the end projection for each region is weighted 60% observed regional data, 40% 2021 baseline with proportional swing.
4. Normalise vote shares so they sum to 100%.

Constituency Projections

1. 2024 UK general election results for Scotland are re-mapped to SPC boundaries to provide a realistic baseline for Reform UK (who had negligible 2021 Holyrood vote share).
2. Apply proportional swing from regional projections to 2021 notional constituency baselines, using each constituency's share of the regional vote as the within-region distribution. For Reform, use remapped 2024 Westminster figures as baseline. For Greens, apply national proportional swing only in constituencies where they are standing. Normalise to 100%.

Seat Allocation

Based on constituency and regional projections, overall seats are calculated using the D'Hondt system. 73 constituency seats are allocated by First Past the Post. 56 regional list seats (7 per region) are allocated via D'Hondt, which compensates for disproportionality in the constituency results.

Limitations

Projections involve inherent uncertainty — they are estimates based on uniform swing assumptions and may not reflect local factors. They are not predictions of the final result. Seats within a 5 percentage point margin are flagged as "too close to call."