Another thought I have about all this is that, in general, large swings and unpredictability are BAD for business. Everyone feels it is safe to invest when conditions are stable, even if costs may not be as low as they might like. But in an unpredictable world, a lot of enterprises cannot plan, cannot therefore optimise - and we end up with a sub-optimal economy across the board. We do seem to be suffering from a lot of uncertainty at present, whether it be the future intentions of KSA or Iran (or Brazil or Venezuela, come to think of it), or the US election farce, or Putin's games in the Middle East and the effect of the refugee crisis on the EU. Also I still have the feeling that the Chinese are due for a shake-out of their various bubbles........
I'm sure all this is weighing on economic growth prospects - as of course will be the cost of the investments that have gone bad as a result of various commodities, including oil, dropping in price at the end of the China boom.