In portfolio optimization, when having negative KPIs, what does it mean to select a subset of projects with contributions that result in a KPI end value to be less than 0?
For example, if we have below KPI:
- KPI : reduce order to ship time.
- baseline : 5 days.
- end target : 3 days.
and our optimizer selected a subset of projects in which two of them contributed to the above KPIs as follows:
- project A: reduced shipment time by 4 days.
- project B: reduced shipment time by 2 days.
which results in KPI value 5 - 6 = -1.
Is this an acceptable practice "because it is obvious time will always be greater than 0"? Or should we constrain our optimizer to have KPI values above zero but in return select a subset of projects with higher total cost?