Method and apparatus for creating due-to reports for activities that may not have reference value

Methods and apparatuses for computing a variance for the difference between two business metrics. In one embodiment, the method accesses a response model and a plurality of activities with start and end values for each of the plurality of activities. Furthermore, the method computes a variance for the difference between the first and second business metrics for each of the plurality of activities using the response model by setting that activity to one of the corresponding starting and ending values and setting others of the plurality of activities to the value state opposite of that activity, wherein the variance for an activity is the change in contribution for that activity between the start and end sales volumes.