End of the Palladium surge?

In comparison to non-ferro base metals in general, but also to the other precious metals, the gold price is much less volatile. As such it makes sense to compare other metals to gold in a ratio.  The Au/Pt ratio tells how many ounces of platinum an ounce of gold buys and similarly for the Au/Pd ratio. The below chart shows that Palladium got more expensive vis-à-vis gold over the past months.
The Platinum to gold ratio has been trending sideways, implying that platinum moved in closer relationship relative to gold.

The lower dynamic range of the Au-Pt ratio over the past seven months (since early May-2017) cannot be extrapolated to the past. Only since 2015 platinum has constantly been less expensive than gold. In a historic perspective this almost seems anomalous. But is this indeed temporary or will the palladium prices exceed that of platinum for months or years to come?  The more the price gap gets wider, the more probable it is for palladium to remain consistently more expensive than platinum.