"Causes of the Oil Shock of 2007-08"

Prof Hamilton at Econbrowser comments on his latest paper on the oil shock of 07-08. He notes that while world GDP and oil demand grew strongly from 03 to 07 world oil production stagnated between 05 and 07 and hence the price of oil had to increase to persuade some to curb consumption.
He then explains: "It seems reasonable to maintain that the economic growth in 2006 and 2007 would have resulted in at least as big a shift of the demand curve as resulted from the slightly weaker GDP growth of 2004 and 2005. Adding in the first half of 2008 (when global GDP continued to rise), consider then the consequences of a rightward shift of the demand curve of 5.5 million barrels per day. With production only increasing by 0.5 mb/d over this period, a demand elasticity of ε = 0.06 would imply that the price should have risen from $55/barrel in 2005 to $142/barrel in 2008:H1.

"But why then did the price subsequently collapse even more dramatically? A shift of the demand curve back to the left as a result of the impressive global economic downturn is certainly part of the answer. Note, however, that even if global real GDP were to fall by more than 10%-- which so far fortunately it has not-- that would only put us back to where we were in 2005 (at $55 a barrel), and the price was observed to fall even more than this. We therefore would need to postulate a second factor behind the price decline of 2008:H2, namely, an increase in the price elasticity of demand as consumers had time to make adjustments. Again such a hypothesis is consistent with previous experience, and in particular, between 2007:Q3 and 2008:Q3, U.S. petroleum consumption fell by 8.8%. That drop in U.S. petroleum consumption unambiguously represented the combined effects of lower income and price-induced changes in use.

If we say that one elasticity (0.06) is to be used to account for the 2008:H1 price and another higher elasticity for 2008:H2, there is an implicit claim that market participants were learning imperfectly about the price elasticity of demand. There was a surprisingly long period in which demand responded less than some might have expected to the oil price increases (i.e., consistent with an elasticity of 0.06), and then a very dramatic drop in oil use as a result of the combined influence of falling incomes and changing consumption habits."

But where are the speculators?