Srhink Factor

Is there a way to configure the system so that the system will calculate the yield quantity instead of the start quantity?  Currently, when entering a WO header quantity, the system adds shrink % to that quantity to derive start quantity (i.e. order qty + shrink).  This is the quantity MRP uses to plan for lower-level components' requirements.  Is there a configuration that will allow the system to calculate yield quantity instead (i.e. order qty - shrink)?  MRP will plan to WO header quantity for lower-level components' requirements?