Why is global trade so weak?

Global trade is awful. Really, it is. For the last five years, trade volumes have been growing at their slowest sustained rate since the early 1980s. Here's a horrible chart from the World Trade Organisation's latest forecast: And in the last year, things have got worse: Import demand of developing economies fell 3.2% in Q1 before staging a partial recovery of 1.5% in Q2. Meanwhile, developed economies recorded positive import growth of 0.8% in Q1 and negative growth of -0.8% in Q2. Overall, world imports stagnated in the first half of 2016, falling 1.0% in Q1 and rising 0.2% in Q2. This translated into weak demand for exports of both developed and developing economies. For the year-to-date, world trade has been essentially flat, with the average of exports and imports in Q1 and Q2 declining 0.3% relative to last year. Oh great. The WTO's chart shows that flat trade eventually translates into flat growth. And as this chart from the World Bank shows, gro...