Measuring the Regional Economic Cost of Brexit: Evidence as of 2026

This paper examines the regional distribution of Brexit's economic costs across the United Kingdom. We apply a synthetic control approach to two complementary outcomes - real gross value added (GVA) and nominal gross disposable household income (GDHI) - covering multiple levels of UK spatial aggregation. We construct placebo-weighted ensemble counterfactuals using both post-2016 and post-2020 treatment windows. We document three main findings. Economic losses are large and geographically widespread: around 70% of local authority districts record output or income below their synthetic counterfactual. Losses are unevenly distributed. They are concentrated in initially prosperous and trade-integrated regions, particularly London, the South East, and Scotland, while less affluent areas experience comparatively smaller declines. This pattern is consistent with a process of "levelling down": Brexit has reduced regional inequality not by improving economic performance in lagging areas, but by disproportionately weakening leading ones. Northern Ireland is a clear exception, having been partly insulated from these losses by its continued access to key elements of the EU single market. (Previously titled: "Measuring the Regional Economic Cost of Brexit: Evidence up to 2019" Revised June 2026)