By SIMON CONSTABLE
Stock investors might need to look out below.
An esoteric financial markets indicator just registered a warning signal that historically augured in double-digit falls in the S&P 500, the index tracked by the SPDR S&P 500 (SPY) exchange-traded fund.
The metric in question is the Marshallian K., which measures the liquidity in the economy. Recently, the liquidity started contracting. Read more here.