Instead, Spain must achieve "internal devaluation" : it must cut wages and prices until its costs are back in line with its neighbors.

But if higher prices are matched by rising wages in China, the result could also be that China drives more of its growth from internal demand, as consumers have more money to spend.

An internal Overstock survey revealed during the trial found that its reference prices were on average 15 percent higher than the highest price that could be found online.