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.
According to a May 2003 study, increasing the amount of ethanol to our gasoline pool could reduce the cost of fuel to consumers by as much as 6.6 cents per gallon. The American Petroleum Institute has estimated that the presence of ethanol causes gasoline prices to be 27 percent lower compared to regular unleaded.