Here's a DOE official paper about oil shale which claims the US has 2 trillion bbl (whatever a bbl is) of oil shale out of the world's 2.6 trillion bbl.
http://fossil.energy.gov/programs/reserves/npr/NPR_Oil_Shale_Program.html
http://fossil.energy.gov/programs/reserves/publications/Pubs-NPR/40010-373.pdf
The report linked by pawns is obviously "sensationalist" and I don't trust it in the slightest, but there may be some substance to what they are saying.
that's like stangbo saying 90% of world's serial killers (or whatever number he said) are in the US.
maybe 60 percent of the statistics collectors are in the US, and 80 percent of the petroleum statistics collectors. we need a coefficient that relates the number of statisticians with any statistic for a given country.