Research preview

The Korean equity market experienced a sudden 8% drop, triggering a trading halt and exposing vulnerabilities in market microstructure and risk models. This article examines the event through the lens of quantitative investment theory, focusing on price impact, liquidity risk, and portfolio resilience. Market Microstructure and the Role of Bid‑Ask Spreads When a market moves sharply, the bid‑ask spread widens, reflecting heightened uncertainty and reduced depth. A simple illustration is a bid of 99.95 and an ask of 100.05, which creates a round‑trip cost of 0.10 per unit before any price move....