Despite hopes that negotiating its own trade agreements would boost the U.K. economy, even the worlds' biggest countries won't serve as a magic trade bullet. For example, the U.K.'s trading relationship with China is much smaller than you'd expect. Signing a good trade deal won't be the transformative move that pro-Brexit supporters are expecting, according to a new report by the Institute for Fiscal Studies. Even if British exports to China grow by 10% annually over the next 15 years, this still won't come close to levels seen with Britain's top trading partners: the United States and the European Union....