You posted a 6 month chart which doesn't show it well. Here is your exact chart only with two years data showing. You can see the double bull ETF:UCO outperformed the single bull ETF:USO right up until the broad market high in early May/11. Then the UCO tracked the USO evenly all the way down into the selloff to the early Oct low. From Oct until now the double bull UCO has been underperforming the single bull USO despite being double even in the uptrend as well as this downtrend. The point being one must be careful of what they 'assume'........................