"Even if no organisation is perfect, anyone who believes they can rely on a system of bilateral trade agreements instead of the WTO risks enormous losses of prosperity in international trade," said Bertelsmann trade expert Christian Bluth.
With 164 member countries, the WTO will celebrate a rocky 25th anniversary on January 1, 2020. Washington refuses to name new judges to its appellate body, blocking arbitration of trade disputes.
Washington and Beijing have nonetheless struck a truce in their tit-for-tat tariff war, hoping to sign a preliminary trade deal in January. Around the world, Bertelsmann found WTO members gained on average 4.5 percent of GDP from membership. The total increase reached $855 billion or one percent of global output, the study showed.
And around the world, WTO members' exports increased an average of 14 percent between 1980 and 2016, while non-members' exports fell almost six percent. So far, "nations with strong exports and production are the main beneficiaries" of WTO membership, the Bertelsmann Foundation said in a statement, pointing to countries such as South Korea and Mexico as further winners.
European countries with smaller manufacturing sectors have not been able to make such large gains from WTO membership. France's output was boosted by $25 billion, while Britain's added $22 billion - both well below the average increase of 4.5 percent of GDP.
European Commission president Ursula von der Leyen has said she planned to meet US President Donald Trump "at the beginning of 2020", with trade one of the major issues on the table.