Non-monotonic NPV Function Leads to Spurious NPVs and Multiple IRR Problems: A New Method that Resolves these Problems

The causes and effects of non‐monotonic NPV functions are evaluated and the results presented in this paper. Reinvestment of intermediate income causes non‐monotonic NPV function. Non‐monotonic NPV function not only leads to multiple IRRs but also to spurious NPVs. The capital amortisation (CAS) method used in this analysis transparently reveals if there is any reinvestment. A modified CAS method, discussed in this paper, eliminates the reinvestment and resolves the problems of non‐monotonic NPV function, reinvestment, spurious NPVs and multiple IRR. The current practice of using NPV as the preferred criterion, when there are multiple IRRs, is not appropriate.