How big is global trade?

World exports of manufactured goods, agricultural products and fuel and raw materials were worth about $15.5tn in 2016, according to the WTO. Commercial services such as transport and communications exports were worth a further $4.8tn.

China is the world’s biggest exporter, shipping merchandise worth about $2.3tn, followed by the US with about $1.5tn and Germany with $1.4tn.

Donald Trump often complains that America imports far more than it sells around the world, which is known as a trade deficit. While exports were worth about $1.5tn last year, imports were worth almost $2.4tn, leaving a deficit of more than $800bn.

China accounts for the largest proportion of the US deficit, with Americans buying about $375bn more from China than they sell in return.

For the UK, the EU is its largest trading partner. The UK imported 55% of all goods from the EU and exported 51% to countries outside the bloc in the year to the end of May. The US is the largest single nation for British exports and imports, worth a total of about £90.6bn, led by exports of cars.

The UK ran a trade deficit of about £25.9bn last year. Excluding services – the dominant driver for the UK economy – the UK ran a trade in goods deficit of £137.5bn.

Measuring the value of trade is fiendishly complex. There are several potential problems with data quality, as countries in varying stages of economic development use different ways to collect information. The US and the UK often report trade surpluses with one another, which is impossible.

Research from Deutsche Bank suggests the true size of US business interest in China is not captured by the US Census Bureau figures because it does not include the sale of goods and services by American multinationals. With these added Deutsche Bank said the US would have a surplus of $20bn with China and an overall surplus of $1.4tn with the world.

Trade in services complicates matters further. While working out the value of a widget arriving ashore is easy, assessing where exactly the value of an internet download originates is trickier.

Globalisation has also made it less likely that goods are made in just one place. Components are brought together from different countries, further complicating the assessment of exports and imports.