NO.PZ201710100100000301
问题如下：
1. Holding all else constant, the change in Blake’s income will most likely result in:
选项：
A.an increase in his marginal utility of consumption.
B.an increase in his intertemporal rate of substitution.
C.a decrease in his required risk premium for investing in risky assets.
解释：
C is correct.
The additional annuity payment substantially increases Blake’s income and wealth, which decreases his marginal utility of consumption. As a result, the average loss of marginal utility from any risk taking decreases as his wealth increases. Thus, he requires a lower risk premium and is willing to buy more risky assets.
考点： intertemporal rate of substitution
解析：遗产投资到了年金，年金使得未来收入增加。
A，收入增加，基本的生活需求已经被满足，那么消费带来的爽度减小，所以 marginal utility of consumption减小。
B，m=MUt+s/MUt ，未来收入增加，使得MUt+s减小，所以最终m减小。
C选项可作为新的结论来记：收入增加，MUt+s减小，假设投资风险产品有亏损，由于MUt+s本身是一个比较小的数值，那么亏损带来的爽度的减少也很小，所以投资者愿意承担风险（即使投亏了，也觉得没什么影响），所以对于承担风险要求的补偿也比较低。
请问B选项中，MUt+s指的是什么呢？为什么未来收入增加，这个值会变小呢？
