`  == Disjointed facts/stats ==  Is anyone else baffled by this sentence?:  ``The Alberta deposits contain at least 85% of the world's total reserves of natural bitumen but are concentrated enough to be the only deposits...``  What does the ``but are...`` clause mean?  It doesn't make any sense to me.  Also, that 85% statistic seems incompatible with the subsequent one on Venezuela: ``...the Orinoco oil belt vies with the Canadian oil sand [sic] for largest known accumulation of bitumen in the world.``  If Venezuela's vies with Canada's, that would add up to, um, somewhere around 170% in total?  If this mathematical impossibility is due to a difference in definition between ``reserves`` and ``accumulation``, then can someone please repair this inappropriate comparison of apples and oranges?  Perhaps ``apples and oranges`` is responsible for this apparent contradiction too:  ``Venezuela prefers to call its oil sands ``extra heavy oil``, and although the distinction is somewhat academic, the extra heavy crude oil deposit of the Orinoco Belt represent [sic] nearly 90% of the known global reserves of extra heavy crude oil.``  Please, either the distinction is meaningful or it isn't.  If it is, then please clarify the confusion.  If it isn't, then we've got 85% of the reserves in Canada, and 90% of the reserves in Venezuela, for a total of 175%.   `