  Gold and currency markets form a unique pair with specific interactions and
dynamics. We focus on the efficiency ranking of gold markets with respect to
the currency of purchase. By utilizing the Efficiency Index (EI) based on
fractal dimension, approximate entropy and long-term memory on a wide portfolio
of 142 gold price series for different currencies, we construct the efficiency
ranking based on the extended EI methodology we provide. Rather unexpected
results are uncovered as the gold prices in major currencies lay among the
least efficient ones whereas very minor currencies are among the most efficient
ones. We argue that such counterintuitive results can be partly attributed to a
unique period of examination (2011-2014) characteristic by quantitative easing
and rather unorthodox monetary policies together with the investigated illegal
collusion of major foreign exchange market participants, as well as some other
factors discussed in some detail.
