An international agreement forecast to boost global trade by $1 trillion (£800bn) a year has come into force.
The Director General of the World Trade Organization (WTO), Roberto Azevedo, called it "the biggest reform of global trade in a generation".
The Trade Facilitation Agreement (TFA) involves streamlining customs procedures.
Mr Azevedo said it would have a bigger impact than eliminating all existing taxes on imports, known as tariffs.
It involves countries signing up to a long list of reforms, including easier access for businesses to information, reduced fees and simpler and faster procedures.
WTO economists estimated it would cut the cost of trading by 14.3%, and that developing nations would gain the most.
TFA is one of the few successes of a much wider set of negotiations that were launched in late 2001 in the Qatari capital and known as the Doha Round.
It is not the only product of the Doha Round, but most of the negotiating agenda ran into the sand.
Questions
1. Using a diagram, explain how tariffs restrict world trade
2. Using AD/AS explain how exports stimulate growth
