One of the most critical factors that investors look for in a financial market is liquidity. Liquidity is defined as the ability to buy or sell significant quantities of a security quickly, anonymously, and with relatively little price impact. Lack of liquidity was the fundamental cause of the recent global financial crises. This occurred because the liquidity measures in academic literature were not able to detect the problem due to theoretical and empirical flaws. In this lecture, Professor Andros Gregoriou presents a new liquidity measure that is superior to previous theoretical models and was able to detect the global financial crises.