Arch Models ((link)) Link

This matches reality. After the COVID crash in March 2020, the VIX (fear index) stayed above 25 for nearly six months. 1. Risk Management If you assume volatility is constant, your Value at Risk (VaR) will be wrong 90% of the time. GARCH models give you dynamic VaR—higher during crises, lower during calm periods.

If you have ever tried to predict stock market volatility, you have run into a frustrating reality: arch models

If you work in trading, risk, or quantitative finance, GARCH(1,1) should be as familiar to you as linear regression. It is the baseline—the "check your assumptions" model for anything involving volatility. This matches reality

Enter (introduced by Tim Bollerslev in 1986). A GARCH(1,1) model—the industry workhorse—uses only three parameters to capture volatility dynamics: Risk Management If you assume volatility is constant,