The message yesterday from the world’s leading authorities on trade was clear: official data no longer reflect the realities of the global economy.

The World Trade Organisation and the Organisation for Economic Co-operation and Development were equally explicit in pointing out that their more accurate “value-added” figures changed the debate on trade policy. The “value-added” approach used by the WTO and OECD in their year-long research project highlights the fragmented and global nature of manufacturing processes. The research adds weight to arguments in favour of more openness on trade. Because the supply chain for products is now often global, exporters’ success in international markets depends not just on their capacity to make the finished product but on their ability to import the materials used in its manufacture.

For goods produced globally, high tariffs and other barriers on imports act as a tax on exports, jeopardising economies, and jobs, rather than protecting them. “Protection measures against imports of intermediate products increase costs of production and reduce a country’s ability to compete in export markets,” the OECD and WTO said.