1,272 research outputs found
Stochastic Nonparametric Envelopment of Data: Combining Virtues of SFA and DEA in a Unified Framework
No full textThe literature of productive efficiency analysis is divided into two main branches: the parametric Stochastic Frontier Analysis (SFA) and nonparametric Data Envelopment Analysis (DEA). This paper attempts to combine the virtues of both approaches in a unified framework. We follow the SFA literature and introduce a stochastic component decomposed into idiosyncratic error and technical inefficiency components imposing the standard SFA assumptions. In contrast to the SFA, we do not make any prior assumptions about the functional form of the deterministic production function. In this respect, we follow the nonparametric route of DEA that only imposes free disposability, convexity, and some specification of returns to scale. From the postulated class of production functions, the proposed method identifies the production function with the best empirical fit to the data. The resulting function will always take a piece-wise linear form analogous to the DEA frontiers. We discuss the practical implementation of the method and illustrate its potential by means empirical examples.Productivity Analysis,
The Portrayal of Family and Self-reflexivity in Luigi Pirandello’s Six Characters in Search of an Author
No full textLuigi Pirandello’s play, Six Characters in Search of an Author (1921, Sei personaggi in cerca d’autore)
portrays numerous significant and functional characteristics of metatheatre, a concept coined by Lionel
Abel. By drawing on such metatheatrical features and the play within a play technique, Pirandello’s play
presents six characters that are in search of an author. This study will, therefore, explain the concept
of metatheatre and present a critical analysis of the play, Six Characters as a self-reflexive play. In this
critical engagement with the text through specific references from the play and relevant secondary sources,
important themes in the play such as reality and illusion, life, art, and the representation of the family in the
play will be analysed. This analysis will ultimately demonstrate that Pirandello presents six characters that
are self-conscious of their position as dramatic characters that manage to act out their roles, which actually
reveal the family relationships between the characters
Double bootstrap confidence intervals in the two-stage DEA approach
No full textContextual factors usually assume an important role in determining firms' productive efficiencies. Nevertheless, identifying them in a regression framework might be complicated. The problem arises from the efficiencies being correlated with each other when estimated by Data Envelopment Analysis, rendering standard inference methods invalid. Simar and Wilson (2007) suggest the use of bootstrap algorithms that allow for valid statistical inference in this context. This article extends their work by proposing a double bootstrap algorithm for obtaining confidence intervals with improved coverage probabilities. Moreover, acknowledging the computational burden associated with iterated bootstrap procedures, we provide an algorithm based on deterministic stopping rules, which is less computationally demanding. Monte Carlo evidence shows considerable improvement in the coverage probabilities after iterating the bootstrap procedure. The results also suggest that percentile confidence intervals perform better than their basic counterpart.Peer reviewe
New Models for Data Envelopment Analysis. Measuring Efficiency Outwith the VRS Frontier
No full textSome models are presented in this paper which extend the concept of measuring superefficiency to the useful case of variable returns-to-scales (VRS), thus enabling the ranking of efficient as well as inefficient units. Two models, namely the Universal Radial Model and the Universal Additive Model, are presented that also have strong invariance properties (units and translation invariance). For both of these models a method for normalising the efficiency scores on a (0-1+) scale is presented. These models have been implemented in a software package and applied to the ranking of units in an industrial context.Data envelopment analysis (DEA), Superefficiency, Universal models
Measuring the relative efficiency of banks using DEA method
No full textData Envelopment Analysis (DEA) is one of the most popular methods used for measuring the relative efficiency of similar units by considering various input/output parameters. This paper implements DEA models to estimate the relative efficiency of selected banks in the United States. The proposed study uses two inputs, total assets and number of employees, and one output, net revenue for measuring the relative efficiency of selected banks. The relative efficiencies of different banks are analyzed. The preliminary results indicate that Santander Bank is the most efficient banks operating in the United States followed by SunTrust Bank and HSBC. Other banks preserve lower efficiency compared with these three banks.Peer reviewedFinal article published.Data envelopment analysis (DEA)EfficiencyBank industr
Stochastic DEA
No full textInternational audienceData Envelopment Analysis (DEA) was introduced as a linear programming model by Charnes et al. (Eur J Oper Res 2:429\textendash444, 1978) and Banker et al. (Manag Sci 30:1078\textendash1092, 1984) as a nonparametric model to estimate frontier production and technical efficiency using linear programming. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG
Basic analytical capabilities of the CCR-DEA model
No full textThe article describes some analytical applications of the basic DEA model – CCR model proposed by Charnes, Cooper and Rhodes [2]. The author presents elementary DEA profiles, terminology, ideas and some traditional ways of determining the optimal technology for inefficient objects and benchmarking and estimating the type and size of returns to scale. The evaluation of input excess and output shortage is also described. In this context, the author suggests an economic interpretation of the optimal solution of the CCR model as a task that consists of creating virtual technology of a given set of objects. The author also presents how to determine the structure of a target and optimal technology and indicates the way of using simplex reports in sensitivity analysis of the solution to the CCR model. All these reflections are illustrated by a real-life DEA problem that concerns bank efficiency.CCR-DEA, interpretation of CCR model, Optimal technology structure
Rice growing farmers efficiency measurement using a slack based interval DEA model with undesirable outputs
No full textIn recent years eco-efficiency which considers the effect of production process on environment in determining the efficiency of firms have gained traction and a lot of attention. Rice farming is one of such production processes which typically produces two types of outputs which are economic desirable as well as environmentally undesirable. In efficiency analysis, these undesirable outputs cannot be ignored and need to be included in the model to obtain the actual estimation of firm’s efficiency. There are numerous approaches that have been used in data envelopment analysis (DEA) literature to account for undesirable outputs of which directional distance function (DDF) approach is the most widely used as it allows for simultaneous increase in desirable outputs and reduction of undesirable outputs. Additionally, slack based DDF DEA approaches considers the output shortfalls and input excess in determining efficiency. In situations when data uncertainty is present, the deterministic DEA model is not suitable to be used as the effects of uncertain data will not be considered. In this case, it has been found that interval data approach is suitable to account for data uncertainty as it is much simpler to model and need less information regarding the underlying data distribution and membership function. The proposed model uses an enhanced DEA model which is based on DDF approach and incorporates slack based measure to determine efficiency in the presence of undesirable factors and data uncertainty. Interval data approach was used to estimate the values of inputs, undesirable outputs and desirable outputs. Two separate slack based interval DEA models were constructed for optimistic and pessimistic scenarios. The developed model was used to determine rice farmers efficiency from Kepala Batas, Kedah. The obtained results were later compared to the results obtained using a deterministic DDF DEA model. The study found that 15 out of 30 farmers are efficient in all cases. It is also found that the average efficiency values of all farmers for deterministic case is always lower than the optimistic scenario and higher than pessimistic scenario. The results confirm with the hypothesis since farmers who operates in optimistic scenario are in best production situation compared to pessimistic scenario in which they operate in worst production situation. The results show that the proposed model can be applied when data uncertainty is present in the production environmen
The discovery of SycO reveals a new function for type three secretion effector chaperones
No full textThe Type Three Secretion (T3S) system is a device used by many Gram-negative pathogens that allows bacteria to deliver effector proteins straight into the eukaryotic cell cytosol. These effectors interfere with various signaling pathways to subvert the host cell functions. The secretion machinery of the T3S system consist of a basal body spanning the bacterial inner and outer membrane followed by a stiff hollow needle outside the bacterium. The fully assembled secretion apparatus constitute a continuous hollow conduit that connects the bacteria to the eukaryotic target cell. After cell contact, virulence proteins -called effectors- are injected directly into the cytosol of the host cell via the T3S apparatus. Several effectors of the T3S system require the assistance of specific cytosolic chaperones to be efficiently exported. There are three classes of T3S chaperones. Effector proteins are assisted by Class I chaperones. Although Class I chaperones are well characterized, their main function is still a matter of controversy. In this thesis, we demonstrate that orf155 encodes a specific chaperone for the effector YopO that we called SycO. We showed that SycO enhances YopO secretion in vitro and is required for translocation of YopO into infected cells. By pulldown assay we demonstrated that residues 20 to 77 of YopO are required and sufficient for SycO binding. Using crosslinking experiments and size exclusion chromatography analysis, we determined the stoichiometry of purified SycO and YopO-SycO complexes. SycO alone forms dimers in solution and the YopO-SycO complex has a 1:2 stoichiometry. These results suggested that SycO is a typical chaperone of the Class I. YopO is a serine/theronine kinase that interacts with Rho and Rac and disrupts the cytoskeleton of the target cells. YopO has been shown to localize at the cell plasma-membrane. By transfection of YopO-EGFP hybrid proteins into HEK293T cells, we demonstrated that the chaperone-binding domain (CBD) coincides with the membrane localization domain of YopO. Nevertheless, the CBD was not needed for the kinase activity of YopO. By ultracentrifugation, we also showed that the CBD causes YopO aggregation in the bacteria, when SycO does not cover it. Further, we show that the CBD of YopE and YopT also caused aggregation in the bacteria in the absence of SycE and SycT respectively. YopE, YopT and T3S effectors in other systems also act at the membrane of the eukaryotic host cell. We propose a new hypothesis concerning the role of T3S chaperones. The sub-cellular localization domain of effectors is aggregation-prone and creates the need for a chaperone inside bacteria. We propose that masking such aggregation-prone localization domains may be a general function for type III effector chaperones
A fuzzy DEA slacks-based approach
No full textThis paper deals with the problem of efficiency assessment using Data Envelopment Analysis (DEA) when the input and output data are given as fuzzy sets. In particular, a fuzzy extension of the measure of inefficiency proportions, a well-known slacks-based additive inefficiency measure, is considered. The proposed approach also provides fuzzy input and output targets. Computational experiences and comparison with other fuzzy DEA approaches are reported.The first author was partially supported by the research project MTM2017-89577-P (MINECO, Spain). The second author was partially supported by the Spanish Ministry of Economy and Competitiveness, grant AYA2016-75931-C2-1-P and from the Consejería de Educación y Ciencia, Spain (Junta de Andalucía, reference TIC-101). The third author acknowledges the financial support of the Spanish Ministry of Science, Innovation and Universities, grant PGC2018-095786-B-I00
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