In both samples, accounts run with input from financial advisors offer lower returns than those run by similar investors without such input.

FORBES: Why Advisors Don't Add Value

According to ITF statistics, Tipsarevic was among the minority of players who had to provide samples both in competition and outside of it in 2012.

CNN: Tennis is a 'clean sport,' says Tipsarevic

But because they use different samples the figures sometimes diverge, in terms of both the monthly price changes and annual trends.

BBC: House price surveys explained