There is a consensus that China's economy will slow in the coming years as it transitions away from investment toward consumption and from exports toward domestic sources of growth. There is much uncertainty, however, about how smoothly this transition will proceed and about the policy framework in place to manage any financial disruptions that might accompany it. These uncertainties were heightened by market confusion earlier this year over China's exchange rate policy.

Confusion, that is to say, which was the direct result of the US Dollar soaring to multi-year highs, which forced China, whose currency is peg to said dollar, to aggressively devalue its own currency. 

The rest is history.

And it's not just China: it's every country which, as we warned in November 2014, is reliant on the viability of the Petrodollar, and more importantly, keeping the USD low. Here is Yellen explicitly addressing the impact of collapsing oil prices on oil exporters.