Influential observations in frontier models, a robust non-oriented approach to the water sector

Abstract

Influential observations in frontier models, a robust non-oriented approach to the water sector de Witte, K.; Marques, R.C. Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Download date: 11 May 2018Ann Oper Res (2010) Abstract This paper suggests an outlier detection procedure which applies a nonparametric model accounting for undesired outputs and exogenous influences in the sample. Although efficiency is estimated in a deterministic frontier approach, each potential outlier initially benefits of the doubt of not being an outlier. We survey several outlier detection procedures and select five complementary methodologies which, taken together, are able to detect all influential observations. To exploit the singularity of the leverage and the peer count, the super-efficiency and the order-m method and the peer index, it is proposed to select these observations as outliers which are simultaneously revealed as atypical by at least two of the procedures. A simulated example demonstrates the usefulness of this approach. The model is applied to the Portuguese drinking water sector, for which we have an unusually rich data set.

The Effects of Operational and Environmental Variables on Efficiency of Danish Water and Wastewater Utilities

“…For the wastewater sector, the inputs we used were transport, treatment, and customer handling costs, while the output measure was volumes of water settled in the sewer catchment area. This choice is quite consistent with mainstream literature [1,50] which usually identifies staff costs, operational expenditure, energy costs and mains length as input and the water or wastewater volume and customers served as output. The inclusion of costs among inputs makes it possible to observe the combined effect of any change in purchasing price and operational efficiency.…”

“…For water utilities, outputs (measured by cubic meters of water delivered, or by inhabitants served) remain fairly constant over time, but inputs depend on price fluctuations and internal efficiency. Therefore, most studies in this field and those listed in our literature review used input-oriented models [1,50].…”

Evaluation of Corporate Websites and Their Influence on the Performance of Olive Oil Companies

“…In this model, the output was sales revenue, and the inputs were expenditure on materials and raw materials, personnel expenses, and depreciation of tangible fixed assets [30]. One of the primary weaknesses of this method is its high sensitivity to outliers [49]. To resolve this issue, we used the super-efficiency technique [50], pre-selecting a screen of 2 to eliminate any cases with efficiency scores that were higher than this screen.…”

Estimating the environmental and resource costs of leakage in water distribution systems: A shadow price approach

“…By using the concept of the distance function or directional-distance function (Färe et al, 2006;Tang et al, 2016), a shadow price is calculated for undesirable outputs. Within the urban water supply process, leakage is an undesirable output because they have a negative economic and environmental impact (De Witte and Marques, 2010). Several applications have used the methodological approach proposed by Färe et al (1993Färe et al ( , 2006 to compute the shadow price of different undesirable outputs as a proxy of estimating their environmental cost.…”