Is it possible to have a bid tick that goes down and an ask tick that goes up at the same time? That's to say a down tick for bid and up tick for ask at the same time or when a bid tick is up so will the ask tick and vice-versa

  • B/A spreads can remain constant, widen, or narrow. For the spread to widen, either the bid must drop, the ask must increase, and both can occur as well. May 19, 2018 at 11:44

1 Answer 1


Yes, what would prevent that?

Suppose for a particular asset there's a bunch of people willing to buy at $10 and a bunch of other people (or even the same ones) willing to sell at $20.

Then there's Alice, willing to buy one lot at $14, and Bob, willing to sell one lot at $16.

The bid-ask spread is therefore $14-$16.

Bob decides he really doesn't have time or courage to wait any longer for someone who will pay him $16, and lowers his ask to $14. The exchange matches his order up with Alice's and both orders disappear.

The spread is now $10-$20.


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