Historical ILLIQ
Definition
Amihud (2002) develops a measure of illiquidity of a security at time asWhere is the daily stock return in basis points and is the daily trading value (price × shares traded) in units of 100 million of the stock's trading currency (V-Lab chooses this scaling for readability). ILLIQ is therefore the price move, in basis points, per 100 million traded. Because trading value is in the stock's own currency, ILLIQ levels are comparable only between stocks quoted in the same currency. This measure captures the intuition that a security is less liquid if a given trading volume generates a greater move in its price. It only requires daily data on prices and trading volumes, yet it is highly correlated with other illiquidity measures that require more data inputs.
The historical ILLIQ measure is the 22 trading days (i.e. 1 month) moving average of
References
Amihud, Y. 2002. Illiquidity and stock returns: cross-section and time-series effects. Journal of Financial Markets 5:31 – 56. URL http://www.sciencedirect.com/science/article/pii/S1386418101000246.