Idiosyncratic Volatility

Idiosyncratic volatility is extracted by regressing a security's returns against systematic factors, most commonly a market index or the Fama-French factor model. The residual variance from this regression captures price movements driven by firm-specific events, management decisions, earnings surprises, insider transactions, or sector-specific catalysts. In quantitative insider-trading detection systems, elevated idiosyncratic volatility around insider transaction windows can signal information leakage or opportunistic timing, as informed traders may exploit company-specific developments before public disclosure.

Quant scoring platforms leverage idiosyncratic volatility as a risk-adjusted performance metric and as a surveillance signal. High idiosyncratic volatility may indicate mispricing opportunities or heightened information asymmetry, while anomalous spikes in idiosyncratic volatility preceding insider sales or concentrated purchasing can flag potential market abuse. Cross-sectional analysis of idiosyncratic volatility clustering within PDMR transaction cohorts enhances tipping and shadow-trading detection algorithms.