Dark Pool Liquidity

Mostly run by investment banks, dark pool liquidity refers to large trading volumes in securities...but made on private exchanges that are unavailable to the public.

Banks use supercomputers that can buy or sell millions of shares of a stock in milliseconds, and profits are instantly realized by traders arbitraging minute differences in pricing those securities around the world. Many now believe this provides an unfair advantage in profiting from market gyrations, and should be more closely regulated by the Securities and Exchange Commission (SEC).