> But the EU, as a whole, is the world's biggest market

What metric are you using because the EUs GDP is about 700 billion less than the US and going to drop even more when the UK leaves.

US GDP: http://www.imf.org/external/pubs/ft/weo/2018/01/weodata/weor...

EU GDP: http://www.imf.org/external/pubs/ft/weo/2018/01/weodata/weor...