Your team uses a 500-day Historical Simulation approach for VaR. If the market crashed yesterday due to unexpected rate hikes, but today's calculated VaR barely moved, what could be the reasons? How would you adjust the model?

你的团队用500天历史模拟法计算VaR。如果昨天市场突然发生暴跌（比如由于加息超预期），但今天算出来的VaR几乎没变，你觉得可能是什么原因导致的？你会如何调整模型？