Britain's economy has seen weak growth overall since it left the European Union at the start of 2020, though disentangling the effects of Brexit from the COVID-19 pandemic has been hard for analysts.
Estimates from official bodies and researchers show that Brexit reduced UK GDP by 6-8% by 2025 compared with if Britain had remained in the EU.
Productivity and employment were reduced by 3-4%, while investment decreased by 12-18%.
The weakness was caused by greater business uncertainty, lower expected demand, and slower productivity growth due to the distraction of managing Brexit and its impact on more productive firms that traded internationally.
Calculations were based partly on a 'synthetic' counterfactual UK based on the United States, Estonia, Greece, and Italy, as well as other countries that matched Britain's pre-Brexit economic performance.
Other researchers have criticized the methodology used, arguing that the US economic performance was an outlier and that the UK's GDP per capita growth was similar to Germany and France.
The UK Office for Budget Responsibility estimated that the post-Brexit trading relationship would reduce long-run productivity by 4% relative to staying in the EU.
The UK National Institute of Economic and Social Research estimated a 2-3% loss in GDP per capita and labour productivity by 2023, rising to 5-6% by 2035.
