Trade
The EU is a single market in which no tariffs are imposed on imports and exports between member states. "More than 50 per cent of our exports go to EU countries," says Sky News. Membership of the bloc means we have always had a say over how trading rules are drawn up.
Britain also benefits from trade deals between the EU and other world powers. "The EU is currently negotiating with the US to create the world's biggest free trade area," says the BBC, "something that will be highly beneficial to British business."
Britain risks losing some of that negotiating power by leaving the EU, but it would be free to establish its own trade agreements.