In the previous (nearly) 24 months, the broadest index of the Warsaw Stock Exchange - WIG - has gained more than 20%:
Fig. WIG performance YTD till 2012-12-21; source: stooq.com
This noticeable result has been generated thanks to a pretty small positive drift in daily returns - less than 0.1%:
Fig. WIG daily returns in 2012
Fig. WIG open-close and close-close daily returns
Meanwhile, while the 20%+ WIG's return is quite impressive, it is quite distant from the theoretical maximum gain possible to be realized with perfect prior knowledge.
Fig. Maximum theoretical WIG gain at 1H frequency.