PrepTest 110, Section 3, Question 21
Thirty years ago, the percentage of their income(41 more words not shown)
Which one of the following,(10 more words not shown)
- AThe amount of(18 more words not shown)
- BIn general, single(15 more words not shown)
- CSingle persons today,(19 more words not shown)
- DThe prices of(18 more words not shown)
- EUnlike single persons,(18 more words not shown)
Reading the argument
What if single people have changed what they buy?
Suppose they used to spend freely on steak and lobster, but now buy cheaper food. Food could take up a smaller percentage of their income even if the prices of particular foods have risen faster than their incomes. Their shopping habits would help explain the change. We can't treat a change in the grocery bill as though it must be a change in food prices.
The percentage itself can be a distraction. Going from 20 percent of income to 10 percent doesn't necessarily mean spending fewer dollars. Income has risen, so 10 percent of the new income could be more money than 20 percent of the old income. The author is making a comparison between rates of growth, not simply claiming that food got cheaper.
What we’re looking for
To strengthen that comparison, I'd want to know that we're comparing the same food purchases. If single people still buy the same kinds of food in the same quantities, the falling share of income is much better evidence that their incomes have grown faster than the prices of what they eat.
Working the answers
- A
This keeps the amount eaten constant, but it doesn't keep the kinds of food constant. Someone could eat the same quantity while switching from expensive foods to cheaper ones. Also, the choice concerns food eaten per person generally, whereas the argument concerns single people's spending. A doesn't control their purchases as directly as C does.
- B
Eating less provides another possible reason food takes up less of their income. That makes it harder to attribute the change to incomes outpacing food prices. “Healthier” doesn't settle the cost either; we aren't told what those foods cost. B doesn't remove the shopping-habits concern.
- CCorrect
This gives us a consistent set of purchases: the same kinds of items in the same quantities. Now we can't explain the lower share of income by saying single people simply switched to cheaper foods or bought less.
For that same set of purchases to take up a smaller percentage of income, income must have grown faster than its cost. C therefore supports the author's comparison. It does not require food prices to have fallen; they could have risen while income rose faster.
- D
The prices of other purchases don't establish the relationship between income and food prices. Nonfood prices could rise especially quickly whether incomes outpaced food prices or failed to keep up with them. We still need evidence about the comparison the author actually makes.
- E
Families are a different group. Their food spending might behave differently because of their incomes or purchasing habits. Knowing that their percentage stayed the same doesn't tell us why single people's percentage fell, so it doesn't resolve the problem with the author's inference.
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