The Centre for European Reform estimates that leaving the single market and customs union at the end of December 2020 had reduced UK trade by £7.7 billion, or 11 per cent, in March.
Furthermore, this was on top of a £8 billion, or ten per cent, hit to trade between the June 2016 referendum and quitting the single market, a period which saw a significant fall in the value of Sterling.
The think tank’s analysis in based on creating a “doppelgänger” for the UK trade in goods using data from a group of other similar countries to estimate what would have happened if Britain had stayed in the single market this year – and then comparing that to what has actually happened.
It does not believe coronavirus has significantly affected its model as goods trade in advanced economies has largely recovered to pre-pandemic levels this year.
A similar “doppelgänger” methodology was established to estimate the impact on trade in goods between the In/Out referendum and leaving the single market and customs union.
Last month, the CER estimated the trade blow up to February had been £11.5 billion.
John Springford, CER’s deputy director, said: “There are two reasons why our estimate worsened between February and March.
“Trade growth in the countries that make up our ‘doppelgänger’ UK outstripped Britain’s, widening the gap with our modelled economy that stayed within the single market and customs union.
“The ONS has also revised February’s trade data downwards.”
He added: “It is important to remember that monthly trade data is volatile, so it will take several more months to be certain about the effect of Brexit on the level of UK goods trade, but it is becoming clearer that the impact cannot be dismissed as temporary.”