为什么冬天的波动率会影响夏天的计算呢

问题如下：

The seasonal volatility of gas prices influenced by demand is obvious. In winter, forward prices are highly volatile, while in summer, forward prices volatilities are low. Which of the following descriptions is correct if we use unweighted historical data from the last three years in estimating VAR values?

选项：

A.Overestimates summer VAR, but underestimates winter VAR

B.Both summer VAR and winter VAR are overestimated

C.Both summer VAR and winter VAR are underestimated

D.Overestimates winter VAR, but underestimates summer VAR

解释：

When estimating VaR for summer using unweighted historical data, the high volatility from the winters over the last three years will increase the calculated VaR for the summer. This will result in an overestimation of summer VaR. When estimating VaR for winter using unweighted historical data, the low volatility from the summers over the last three years will drag down the calculated VaR for the winter. This will result in an underestimation of winter VaR.