The claim: Since 1992, 27 other countries have been more successful at exporting goods to the single market than the UK has.
Reality Check verdict: In terms of volumes of sales, the UK has done much better. But if success is measured by the percentage increase in the amount exported, then Mr Johnson is right.
On BBC One's Andrew Marr Show, Boris Johnson was talking about how countries outside the EU have done better at exporting to the single market than the UK has.
"In the 20 years since the 1992 creation of the single market, actually there were 27 other countries not in the EU who have done better than the UK at exporting into the single market goods, and, I think, 21 countries who have done better at exporting services."
The former mayor of London is referring to research published by Civitas (see the table on page 17), which uses Organisation for Economic Cooperation and Development (OECD) trade statistics.
The measure he is quoting is the percentage increase in exports of goods to the 11 founding members of the single market between 1993 and 2011.
Top of the list is Vietnam, which achieved a 544% increase in exports. But it started at a pretty low level, increasing from $73m (£50m) a month to $400m a month over the period.
Number two on the list is Qatar, which has managed a 496% increase to $300m a month. Number three is Ukraine.
But, actually, while the UK came in at number 28 on the ranking of the top 35 in terms of percentage increases, it exported more to the 11 countries than anyone else on the list, including the USA and China.
The comparison for exports of services does not cover the same time period - it is looking at 1999-2010 (you can find it on page 33 of the same document).
On the services, the UK comes in at number 22 in terms of percentage increase, but is second in value of sales (behind the USA).