Difficulty is defined by (a) frequency of use, (b) frequency of spelling pattern, and (c) developmental norms. It is not difficult, then, for teachers to place students with words of appropriate difficulty based on simple measures of instructional level (Schlagal, 1996).
If one assumes that shifts in the supply curve of ethanol are solely due to the changing price of corn, then, up to an ethanol price of $2.90, the price of corn completely determines the price of ethanol. In other words, the price of corn drives the price of ethanol, not the other way around. This is actually quite logical since the amount of ethanol used is essentially fixed; consequently, something else must be driving the price of ethanol.
The average ethanol price for 2007 was lower than 2006, but the 2007 average unleaded gasoline price was higher than 2006. The ethanol average was $2.24 compared to $2.58 (a 13âpercent decrease), and the unleaded gasoline average was $2.23 compared to $1.94 (a 15âpercent increase).