Generally speaking, if the FFER is higher than the one month (and similar) T-bill yield, then money market funds will park their cash in the ORR facility to earn a higher short-term risk free rate. This results in a contraction of US net liquidity.

Conversely, if the FFER is lower than the one month (and similar) T-bill yield, then money market funds will remove their cash from the ORR facility and buy T-bills. This results in expansion of US net liquidity.