Depends on investor mood. Usually, the PPS drops. It's very much like a buyers' market in real estate.
Normally, MMs purchase your shares when there's no buyers and short or use inventory when there's no sellers. For greys, they can close out open short positions but can't make a market. It's matched trading only w/ buyers in the driver's seat. Like in real estate, when sellers' prices are too high for buyers' taste volume dries up.
The price doesn't have to drop, but sellers tend to get nervous and buyers tend to lowball.
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"We simply attempt to be fearful when others are greedy and to be greedy only when others are fearful."
-- Warren Buffett