RAM: A Range Adjusted Measure of Inefficiency for Use with Additive Models,and Relations to Other Models and Measures in DEA

Generalized Efficiency Measures (GEMS) for use in DEA are developed and analyzed in a context of differing models where they might be employed. The additive model of DEA is accorded a central role and developed in association with a new measure of efficiency referred to as RAM (Range Adjusted Measure). The need for separately treating input oriented and output oriented approaches to efficient measurement is eliminated because additive models effect their evaluations by maximizing distance from the efficient frontier (in ₁, or weighted ₁, measure) and thereby simultaneously maximize outputs and minimize inputs. Contacts with other models and approaches are maintained with theorems and accompanying proofs to ensure the validity of the thus identified relations. New criteria are supplied, both managerial and mathematical, for evaluating proposed measures. The concept of approximating models is used to further extend these possibilities. The focus of the paper is on the physical aspects of performance involved in technical and mix inefficiencies. However, an Appendix shows how overall, allocative and technical inefficiencies may be incorporated in additive models.     

Price momentum in the New Zealand stock market: a proper accounting for transactions costs and risk*

We test for recently reported momentum profits in New Zealand using a practitioner technique that we have not yet seen in the academic literature. This technique simultaneously weighs returns, risk and transactions costs at each portfolio rebalance, rather than blindly chasing returns and then accounting for risk and transactions costs after the fact. We reverse the findings of the earlier literature because our gross profits are more than fully consumed once transactions costs are properly accounted for. Although we focus on momentum trading in New Zealand, our practitioner technique is broadly applicable to investigations of trading anomalies.