Question

Difficulty: MediumWeaken

Economist: Five years ago, the municipality of Oakridge instituted a subsidy program covering half the installation costs for businesses that install rooftop rainwater harvesting systems. Over the same five-year period, commercial municipal water consumption in Oakridge dropped by 30 percent. Because the price of municipal water remained constant throughout this period, the subsidy program clearly succeeded in significantly reducing commercial reliance on municipal water.

Which of the following, if true, most seriously undermines the economist's argument?

  1. A
    Commercial businesses in Oakridge that installed the subsidized rainwater systems reported that the systems met over 60 percent of their non-potable water needs.
  2. B
    The municipal utility rate structure in Oakridge included hidden stormwater drainage surcharges that slightly raised total monthly utility expenses for businesses over the five-year period.
  3. During the five-year period, two large beverage bottling facilities that had historically accounted for nearly half of Oakridge's total commercial water consumption ceased operations.Answer
  4. D
    Total residential water consumption across Oakridge increased by ten percent over the same five-year period.
  5. E
    Rooftop rainwater harvesting systems are entirely incapable of filtering collected precipitation to quality levels safe for commercial human consumption without costly post-treatment equipment.

Answer

The argument is most seriously undermined by establishing that during the five-year period, two large beverage bottling facilities accounting for nearly half of Oakridge's commercial water usage ceased operations.
The argument concludes that the subsidy program caused a 30 percent reduction in commercial municipal water consumption based solely on the correlation between the subsidy's implementation and the subsequent decline. The correct answer undermines this causal conclusion by introducing a compelling alternative explanation: the closure of two major beverage bottling facilities that previously comprised nearly half of the entire city's commercial water usage. If those massive consumers closed, total commercial water demand would naturally plummet regardless of whether any other business adopted rainwater harvesting.

Step-by-Step Solution

1
Identify the argument's premises and main conclusion.
Premises: Oakridge subsidized 50% of rainwater harvesting installations five years ago; commercial water consumption dropped 30% over that period; water prices stayed constant. Conclusion: The subsidy program caused the reduction in commercial water reliance.
Weaken questions require isolating the exact claim the author attempts to prove.
2
Identify the underlying logical flaw or causal gap.
The author commits a correlation-to-causation fallacy by assuming that because the subsidy coincided with a drop in municipal water consumption, the subsidy program must be the cause of that drop, overlooking alternative causes.
To weaken a causal argument, one must introduce an alternative explanation, show a confounding factor, or show the effect occurring without the cause.
3
Evaluate the answer choices for new information that provides a viable alternative cause.
The closure of two water-intensive industrial bottling plants directly accounts for the 30 percent decline in commercial water usage without attributing the change to the harvesting subsidies.
Providing a plausible alternative explanation severs the causal link between the subsidy and the observed reduction in water consumption.

Key Concept

Alternative Causal Explanations in Weaken Questions
Estimated Time:1m 15s
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