From 1973 to 1989 total energy use in this country increased less than

OFFICIAL EXPLANATION

We are given the following facts. From 1973 to 1989 total energy use increased less than 10%. During this same period, the use of electrical energy grew by more than 50%. During this same period, the gross national product (GNP) grew by more than 50%. A careful examination of the second sentence reveals that there is no stated connection between the growth of the GNP and the increase in the use of electrical energy. If you assume that the use of electrical energy somehow caused the growth of the GNP, you are guilty of making an unwarranted causal assumption. Because there is no stated connection between the two other than they both grew by more than 50%, any answer that attempts to connect the two is incorrect. Answer choices (D) and (E) can both be eliminated by this reasoning. Now that we recognize that the GNP issue is only a red herring, let us examine the percentages that are given in the stimulus. The 50% increase in electrical energy gives the impression that the jump must have been substantial. But we know from Misconception #6 that a large percentage does not automatically mean a large number. For example, in this problem it is possible that the 50% increase in electrical energy use was a jump from 2 units to 3 units. The possibility that electrical energy use in 1973 was a relatively small percentage of overall energy use directly undermines answer choices (A), as shown by the following example:

1973 1989
Total energy use (in units) 100 109
Electrical energy use 10 15 (in units)
Percentage of total energy use that was electrical 10% 13+%

A close analysis of the chart also reveals that answer choice (B) can be eliminated. In the example, the use of energy other than electrical energy rose from 90 units to 94 units. Although the example disproves both answer choice (A) and (B), obviously you do not have time to make a chart during the test to examine each possibility, so is there a faster way to eliminate the first two answers? Yes—consider the previous discussion point that information about percentages does not tell us about the numbers. With that idea in mind, because the stimulus contains only percentage information (even though there are two percentages), you should be very suspicious of answer choice (A) (which states that the number of electrical units used was greater) and answer choice (B) (which states that the use of non- electrical energy declined) since they both contain numerical information. At the same time, you should be attracted to an answer such as (C) because it contains only percentage information, and as it turns out, answer choice (C) is correct.