Are foreign exchange volatilities (standard deviations) constant over time?Assume RiskMetrics' model with 0.97 and 0.03 weights on the previous month's variance and squared spot rate change, respectively. Calculate conditional standard deviations for the yen/dollar fx rate over the sample period using the unconditional variance of each series as the Dec 1985 starting point. Plot the conditional stdevs as a function of time on a graph.

告诉了美元和日元每个月的spot和Frwd exchange rate yen/dollar，每个月两种货币的利率和通货膨胀率。

Rishmetric model 网上搜索好多种呀，这里到底用啥？

急求高手指点呀。谢谢先。