When it comes to the components of Implementation Shortfall (IS) I understand how to answer the question in nominal dollars but when putting those dollars into a percentage or bps then I get confused. In the two examples that I have seen one way to get into bps is to divide the nominal dollars by hypothetical portfolio (nominal dollars/(Decision price * #shares). Another way I have seen nominal dollars as a percentage or bps is (nominal dollars/(decision price*#shares))*(weighted portion of shares not filled)
Which one is it!!!???