In Massachusetts, researchers at MIT assert that the increased proportion of ethanol in gasoline merely correlated with the declining crack ratio, and did not contribute to it in any causal sense. Instead, they think that changing oil prices drove the change in the crack ratio, and that when those prices are accounted for, the apparent effect of ethanol “simply goes away.”
To further illustrate that the previous study was touting a correlation, not a causal relationship, the researchers conducted what are known in economics literature as “antitests” of that study’s model. By inserting unconnected dependent variables into the model, they found that the model also produced a strong correlation between ethanol content in gasoline and, for instance, U.S. employment figures — although the latter are clearly unrelated to the composition of gasoline.
The previous work also claimed that if ethanol production came to an immediate halt, gasoline prices would rise by 41 to 92 percent. But they does not think that estimate would bear out in such a scenario.