The rationale behind the move was clear enough. The plunge in crude prices along with the relative weakness of the Russian ruble had severely strained Kazakhstan, which is central Asia's largest crude exporter. As a quick look at a chart of the tenge's effective exchange rate makes clear, the pressure had been mounting for quite a while and when China devalued the yuan earlier this month, the outlook for trade competitiveness worsened. 

What might not be as clear (on the surface anyway) is how recent events in developing economy FX markets following the devaluation of the yuan stem from a seismic shift we began discussing late last year - namely, the death of the petrodollar system which has served to underwrite decades of dollar dominance and was, until recently, a fixture of the post-war global economic order.