Autoregressive Conditional Heteroskedasticity
Autoregressive Conditional Heteroskedasticity, or ARCH, is a statistical model for time series data that describes the variance of the current error term as a function of the actual sizes of the previous time periods' error terms. It is the precursor to GARCH models and was the first to formalize the concept of volatility clustering in financial data.
By modeling the variance as a conditional process, ARCH captures the tendency for volatility to be correlated over time. This is fundamental for understanding why financial markets experience bursts of high volatility.
In crypto, where market shocks can lead to rapid cascades of liquidation, ARCH provides a way to quantify the risk of these volatile periods. It remains a foundational concept for any quantitative analyst working with financial time series.
It highlights that volatility is not random noise but a predictable, path-dependent process.