Since the key to weakening an LSAT argument is to focus on the conclusion, it is essential to break down the argument, which is structured as follows:
Premise—From 1996 to 2004, the average family income decreased by 10%.
Conclusion—The ruling party during that time mismanaged the economy.
The opponents’ argument is causal, making it vulnerable to attack:
Ruling party Average family income decreased
To weaken this argument, you can show that an alternative cause led to the observed effect. Or, you can show that the data is potentially misleading. Because there are dozens of alternative causes that can potentially weaken the opponents' position, test makers are asking a Weaken-EXCEPT question: four of the five “rejoinders” (or replies) would directly counter the opponents’ explanation of the decrease in average family income. Whichever answer choice does NOT counter their explanation will be correct.
Answer choice (A): This is the correct answer choice. The fact that family income rose in 1996 is consistent with the observation that it decreased from 1996 until 2004. This answer choice has no bearing on the conclusion of the argument, making it the correct answer choice to this Weaken-EXCEPT question.
Answer choice (B): This answer choice suggests that average family income may have decreased for noneconomic reasons. If so, this would be an alternative cause for the observed effect, weakening the opponents’ argument.
Answer choice (C): Like answer choice (B), this one suggests an alternative cause for the observed effect—international events beyond the control of the country’s government had an adverse effect on family incomes. This weakens the opponents’ argument, and is therefore incorrect.
Answer choice (D): If the average age of household wage earners fell during that time, and younger people tend to earn less, it would be reasonable to expect that the average family income would decrease. Assuming that the ruling party cannot be blamed for the shifting demographics, this answer choice weakens the opponents’ accusations and is therefore incorrect.
Answer choice (E): If policies enacted before the ruling party came to power resulted in the biggest decreases in family income, then the ruling party is not (entirely) to blame for the decreased income. As with answer choices (B) and (C), we have an alternative explanation for the decreased income, weakening the opponents’ position.