When markets whisper: Indices as early warning signals before the Dot-Com, 2008, and COVID crashes

Financial indices often move subtly before crises, offering early warning signals that can be overlooked amidst market noise. This study examines the behavior of major stock indices preceding three systemic shocks: the Dot-Com crash (2000), the Global Financial Crisis (2008), and the COVID-19 crash (2020). Using historical index data, we analyzed patterns of volatility, trend reversals, and anomalies in trading volumes to identify signals that preceded each downturn. The methodology combined descriptive analysis, trend mapping, and anomaly detection to capture both consistent and event-specific signals. Results show that indices not only mirrored growing market vulnerabilities but also highlighted early stress points weeks or months before crises unfolded. These findings underscore the importance of indices as predictive tools, enabling policymakers, investors, and regulators to better prepare for potential disruptions. JEL Classification Codes: G01, G12, G14, G44, G15