XDF蓝皮书第40,我还是不明白*_*

40. Six months or so after getting a video recorder, many early buyers apparently lose interest in obtaining videos to watch on it. The trade of businesses selling and renting videos is still buoyant, because the number of homes with video recorders is still growing. But clearly, once the market for video recorders is saturated, businesses distributing videos face hard times.

Which of the following, if true, most seriously weaken the conclusion above?

D. The early buyers of a novel product are always people who are quick to acquire novelties, but also often as quick to tire of them.

这个怎么就削弱了?

71. One state adds a 7 percent sales tax to the price of most products purchased within its jurisdiction. This tax, therefore, if viewed as tax on income, has the reverse effect of the federal income tax: the lower the income, the higher the annual percentage rate at which the income is taxed.

the conclusion above would be properly drawn if which of the following were assumed as a premise?

A. The amount of money citizens spend on products subject to the state tax tends to be equal across income levels

完全不能理解,一碰到tax的题我就懵了

113. Which of the following best completes the passage below?

the unemployment rate in the United States fell from 7.5 percent in 1981 to 6.9 percent in 1986. It cannot, however, be properly concluded from these satistics that the number of unemployed in 1986 was lower than it had been in 1981, because________.

D. the total available work force, including those with and without employment, increased between 1981 and 1986.

这道题也不是很明白

麻烦大家了....

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40. 要说明不是只要video recorder存在video就卖不好

D:买video recorder的人本身喜欢新奇事物，也很快对新奇事物失去兴趣，那么很快就会对video recorder失去兴趣，以后有没有video recorder就不是他们买不买video recorder的决定因素了

71:annual percent rate = tax amount / annual income

the lower the income, the higher the annual percent rate. 隐含的假设是tax amount对每个人都是一定的

tax amount = money spent on product * tax rate

自然money spent on product对所有人也是一定的

113. unemployment rate = number of unemployed / total workforce

1986年的rate比1981低了，不能说明number of unemployed低了，也就是total workforce是不同的。考虑一下，当rate一定时，total workforce越大，number of unemployed越大，也就可能总的workforce增大了

谢谢running的解答

40题我还不是特明白

主要还是题没看懂,开始不是说lost interest in obtaining videos了吗? 后面为什么又说the trade of business selling and renting videos is still buoyant, because the number of homes with video recorders is still growing啊?

这不是前后矛盾吗

Six months or so after getting a video recorder, many early buyers apparently lose interest in obtaining videos to watch on it. (一个现象)

The trade of businesses selling and renting videos is still buoyant, because the number of homes with video recorders is still growing. But clearly, once the market for video recorders is saturated, businesses distributing videos face hard times. (作者的观点: the business of distributing video 的好坏 与 拥有video recorder的家庭数量, 成正方向. )

要削弱作者的观点, 就是反驳, 这两者之间没有这正方向. 因为有人买了video recorder后, 就没有兴趣去租或买video回家看, 他们只是图一时的新潮.

40题 文中的结论有个assumption 就是现在的buyer 和early buyer 一样也会在6个月后lose interest in obtaining videos

D选项说early buyer因为爱好新奇也就很容易厌倦 强调了early buyer和现在buyer不同  现在buyer也就未必那么快厌倦 否定了assumption 因此削弱了结论