Economic modeling programs used to predict the future trends of financial markets are notoriously unreliable, primarily because of the enormous number of variables that affect the behavior of investors. No computer, even the most powerful and sophisticated supercomputer, is capable of processing the huge amounts of data necessary for even very short-term forecasts. Because there is no known technology that can make a computer fast enough to perform all of the necessary computations, computer models will never be accurate enough to predict market behavior reliably.

Which of the following, if true, most weakens the argument’s prediction?


A. Over the past five decades, the processing capacity of computers has doubled every two years on average.

B. Complex programs can be subdivided and distributed over multiple interconnected computers that work together to perform extremely large numbers of computations.

C. Banks and financial institutions have relied on computers for decades to track market fluctuations and trends for planning purposes.

D. The use of complexity theory has helped economists to create the most accurate models to date for predicting market crashes.

E. Modeling programs run on supercomputers are used by central banks throughout the world to assist in the formulation of national monetary policies.






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Correct Answer: (B)
The question stem identifies this as a Weaken question. The correct answer will give a fact that makes the prediction in the argument less likely to come true.
The prediction is that computer economic models can never be accurate enough to reliably predict the behavior of markets. The reason given is that even a supercomputer cannot be made fast enough to process all of the data necessary to make the modeling programs accurate.
The author’s prediction is based on the limitations of current computer technology. Whenever the argument makes a prediction of what can or cannot happen, look for a weakener that point out a current or future possibility the author has overlooked. In this case, the correct answer choice is likely to point out some technology that will make it possible to perform all of the necessary computations that a supercomputer could not.

Choice (B) points out the possibility of using multiple interconnected computers to process the large numbers of computations that a single computer cannot. This provides a possible means of making the models more accurate. Although it does not disprove the prediction, this fact is sufficient to call the prediction into question. This is the correct answer.

Choice (A) presents a fact about past increases in computer-processing capacity. This is not sufficient to suggest that the trend will continue or that computers will become fast enough to handle the modeling programs.

Choice (C) is outside the scope of the conclusion. The argument is about predicting financial markets, not tracking them.

Choice (D) has no effect on the conclusion. The “most accurate models to date” aren’t necessarily accurate enough to be reliable predictors of market behavior.

Choice (E) has no effect on the conclusion. The fact that central banks use models in formulating monetary policy says nothing about how the models are used or about the accuracy or reliability of the models used.
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Thank you to all who shared your thoughts on this question! Souvik101990 has shared our official explanation, but answer choice A received so much attention that I wanted to comment on it specifically. Information about computers doubling in speed in the past cannot be presented as evidence that they will continue to do so in the future. We cannot say whether or not they are able to continue doubling in speed without making assumptions of our own.

In this argument, much of the evidence is about the inability of a single computer, even a supercomputer, to process the vast number of computations needed. As was mentioned in an earlier post, we take the premises as a given, which in this case is that one computer cannot do the job using known technology. Still, to weaken the prediction that these models will never be accurate, we need to find something beyond a single computer using current technology that will make this possible. That is why answer choice B is correct, offering a combination of computers instead of a single computer to tackle the job.

As you continue on your GMAT journey, I encourage you to revisit the questions from this RATT race in a week or two. Attempting questions a second time can be a powerful tool to reinforce what you've studied.

Best,
Jennifer
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