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.
Ethanol was supposed to be good for the environment, lower gas prices and increase energy security but the costs of the unintended consequences may outweigh the benefits. Before the ethanol mandate in 2006, corn sold for $2.28 per bushel. Last year it was $6.15 per bushel.