Here you go. The EU is shrinking as a percentage of the world economy.
https://fullfact.org/europe/eu-has-s...world-economy/
As for trade deals, the EU is notoriously bad at agreeing and ratifying them. Noel you don't need to worry about walking away from an existing deal with China, because the EU doesn't have one. Switzerland on the other hand does. The reason the EU is poor at agreeing free trade deals is because it has to try and accommodate the interests of 28 different countries. Sometimes even individual regions have to have their say. The EU Canada trade deal was nearly scuppered by the Belgium region of Wallonia.
Furthermore very few of the trade deals the EU has negotiated include services, which as we know is where the UK is strong. Britain going it along can negotiate trade deals that do include services by offering in exchange tariff free access to its huge consumer market.