问题如下：
2. The events of 2004 to 2006 would be expected to:
选项：
A.bias the historical equity risk premium estimate upwards.
B.bias the historical equity risk premium estimate downwards.
C.have no effect on the historical equity risk premium estimate.
解释：
B is correct.
The events of 2004 to 2006 depressed share returns but 1) are not a persistent feature of the stock market environment, 2) were not offset by other positive events within the historical record, and 3) have led to relatively low valuation levels, which are expected to rebound.
老师这个ERP我有点不理解，如果risk高那么ERP的补偿应该高啊，这样子才有人去投资stock，如果按照解释的说法
“内战时期股票市场的收益率很低，所以我们可以将实际的收益数字带进上述公司，倒推出一个ERP（r低，倒推的ERP自然也低，所以就是这道题的答案，有一个向下的偏差）。然而内战的国家风险很高，投资会要求回报率高即要求一个很高的风险补偿，我们用真实数据倒推得到的ERP（太低了）补偿投资者，他们肯定不干。所以我们要对ERP进行调整（upward adjustment）.”
如果要调整如何调整呢？ERP=Rm-rf，公式里的Rm和rf都是确定的啊。。。
