The Weighted Internal Rate of Return (WIRR) and Expanded Benefit-Cost Ratio (EB/CR)

The purpose of this paper is twofold: the first purpose is to tell a naive history of an experience in constructing knowledge. In this first part I tell how I approached the process to solve the inconsistency between the net present value, NPV, the internal rate of return, IRR and the benefit-cost ratio B/CR or profitability index. There are improvements and drawbacks, mistakes and successes. I think this is important for our students because sometimes they might believe that discovering new ideas or new approaches is an insurmountable job. Sometimes it is, but they have to learn that this is a cumulative process with advances and drawbacks and sometimes it is necessary to start again and start from scratch. The second purpose is to study the development of a procedure to include the implicit assumptions of NPV in the IRR and the profitability index (benefit-cost ratio B/CR). The resulting indicators are named the weighted IRR (WIRR) and the expanded B/CR (EB/CR). These two desirability measures have the property to coincide with the NPV ranking for investment analysis and hence, will maximize value. Examples are presented.