Purchasing Power Parity (PPP) can be used to determine domestic currency power between two rival nations.
Purchasing Power Parity (PPP) serves as an economic theory used in determining the amount of adjustment required between the exchange rate of two countries when purchasing similar goods. This can have an effect on both domestic currencies in question as well as supply-and-demand of the goods in question. The equation allows for calculating the same price of a specific item across two domestic currencies and can therefore be used to determine the relative value of other goods.
The data presented below is through 2017. Values presented in $USD.