The global economic 'canary in the coal mine' hasn't looked this sick since the Great Recession

South Korea's exports dropped by a huge 10.9% in dollar terms between May 2014 and May 2015, the biggest annual drop since the depths of the Great Recession in August 2009.

South Korean exports are a huge deal, and several economists view this figure as a global economic "canary in a coal mine". Korean export data comes out very early compared to other major data releases, and Korea counts the huge economies of China, Japan, Europe, and the United States as major partners. That makes Korea's big export-focused industries a good barometer for the rest of the world.

There are several issues contributing to this slowdown, like the plunging value of the Japanese yen, which has made Korean exports less competitive relative to Japanese exports.

"However, if a weak yen was helping Japanese exporters to gain market share over their Korean competitors, then we might have expected to see Korean exports underperform exports from the rest of Asia. In fact, exports from the rest of the region have performed just as badly as Korean exports over the past few years," Capital Economics' Gareth Leather said.

And what about the strong US dollar distorting the actual value of traded Korean goods? Despite confounding factors, Leather pointed out that "although the fall in Korean exports has been exacerbated by the strength of the US dollar, even in local currency terms exports were still down by over 3% last month."

"Subdued global demand, rather than the strength of the Korean won against the Japanese yen is to blame for the poor recent performance of Korean exports," Leather said

Here's a chart showing this year's weakness: