NO.PZ2020012102000007
问题如下：
Describe the main issues that arise when conducting historical analysis of real estate returns.
选项：
解释：
Properties trade infrequently so there is no data on simultaneous periodic transaction prices for a selection of properties. Analysis therefore relies on appraisals. Secondly, each property is different, it is said to be heterogenous. The returns calculated from appraisals represent weighted averages of unobservable returns. Published return series is too smooth and the sample volatility understates the true volatility of returns. It also distorts estimates of correlations.
解析:房地产交易不频繁，因此没有选择房地产的同时定期交易价格的数据。因此，分析依赖于评价。其次，每个属性都是不同的，它被称为异质的。从估价中计算出的收益是不可观察到的收益的加权平均数。公布的收益序列过于平滑，样本波动率低估了收益的真实波动率。它还扭曲了对相关性的估计。
Return calculation from apprisal deos not in general bias the mean return.为什么这句话答案里没有写？还是这个观点不重要？
只要问道smoothed data，都认为是同时影响return 和risk 的？
