If there is one thing that gets investors twitchy, it is the fear that China is losing its appetite for US government bonds. As the biggest and most liquid pool of assets in the world, the US Treasury market lies at the heart of the global financial system and allows the American government to finance its trillion-dollar budget deficits. Until recently, China has been the largest foreign official holder of US debt. That is why the latest release of Treasury International Capital (Tic) data, showing that China’s holdings of Treasuries fell by a record amount in December, has caused something of a stir.