Barriers to trade impede clear thinking

There is an economic rule called “the 2:1 rule” that was steadily maintained since the 1950s until 2008. It says that world trade volume grows around twice the pace of global GDP. For example, between 1990 and 2008, global GDP expanded at an annual rate of 3.2% while world trade volume growth was 6.0%. Since 2008 the slump knocked things off course but, until recently, the formula was expected to steadily come back as world economies settled down.