how to we know which algorithm strategy to use?

how do we know whether to use implementation shortfall or VWAP algorithm strategy given urgency level, spreads and average daily volume

IS VWAP

urgency level High (Since IS trades early) Low (trader looks to beat days VWAP)

spreads High (IS reduces delay (implicit) cost Low

Trade size relative to average daily volume low High (Trade over the day)

PS: Basically whether to choose IS or VWAP would depend on relative urgency level, spreads, trade size % of ADV of different stocks…

see 2008 AM q8.

trading size should be small for both. use broker or crossing network for large volume size.

Thnx!

However, I wrote in reference to if only two Algo strategies are in the question i.e IS & VWAP…

thank you sherbeer and rahuls