Cross tolerance is a situation where an individual has a tolerance for a drug and it affects his tolerance for another drug. George's tolerance for barbiturate has affected his tolerance for another barbiturate.
The European Union is one of the world's most open economies.
The EU is also the largest single market in the world.
Free trade between Member States is one of the fundamental principles of the EU, so the EU is also committed to liberalizing world trade.
From 1999 to 2010, EU external trade doubled and now accounts for more than 30% of EU gross domestic product (GDP). The EU is responsible for Member States' trade policies and negotiates agreements with them. In international trade negotiations, the EU's single appearance has more influence than individual Member States.
