Implementation Shortfall confusciousssss

So schweser describes one of the components of Imp Sh. as the Delay or slippage costs. In the description they define it as the difference between the closing price on the day the order was not filled and the previous day’s closing price - weighted by the portion of the order that is not filled. however…in their example - Book 5 Pg 124 (and the sauce) they use the formula as: Delay costs = (previous day closing price - benchmark price)/benchmark price * (shares purchased/shares ordered) the Formula seems more intuitive to me… in the example they give there is only a one day diff between the time the order is placed and when it gets fulfilled…so the benchmark price is the same as the “previous days closing price” from the definition… but what if there is a lag of 2 days … then the definition doesn’t seem correct…wouldn’t it be correct to then take the closing price of the day the order was not filled - benchmark price weighted for the filled part… does that make sense?

If you want to make sure, I remember one of the CFAI problems from that chapter had 2 days in between…don’t recall the outcome and don’t have my book w/ me.

I remember that one too. The way they derive the answer is nothing like schweser. More intuitive.