Probably around $5/bbl worth is from the dollar dropping a bit, but the rest is just speculation. I dunno why the author didn't mention this, but the STEO table browser has month by month data on oil supply and demand going back to 1994 or something. I think one out of the last five quarters have had a large gap between supply/demand. At least the 2008 price increase was preceded by something like 8 straight quarters of demand being greater than supply.