The ongoing POMO program is called “Operation Twist”. The FED is purchasing shorter-dated bonds ( 1,2,3 years) and selling the longer dated (20-30 years) variety. This is depressing interest rates and yields, making riskier asset classes (equity) more attractive. Cost of margin interest is also lower and that’s about the only sure long lasting effect on liquidity. The calendar effect of purchases and sales has mostly an intraday and ultra short term liquidity effect.
Billy