Take a look at the “manual adjustment” higher in 2014. To me it says they wanted to take the power off the US recovery, or economy, put stimulation on hold, and give the other countries a weaker currency advantage “spin”.
At the beginning of 2017, TPTB reversed that process, put the others on “hold” and rotate back to supporting the USA export businesses. There are no natural market forces until things get out of hand like the summer of 2008. That there WAS a natural market force against the “master”.