A revised Tobit procedure for mitigating bias in the presence of non-zero censoring with an application to milk-market participation in the Ethiopian highlands

Fixed transactions costs that prohibit exchange engender bias in supply analysis due to censoring of the sample observations. The associated bias in conventional regression procedures applied to censored data and the construction of robust methods for mitigating bias have been preoccupations of applied economists since Tobin [Econometrica 26 (1958) 24]. This literature assumes that the true point of censoring in the data is zero and, when this is not the case, imparts a bias to parameter estimates of the censored regression model. We conjecture that this bias can be significant; affirm this from experiments; and suggest techniques for mitigating this bias using Bayesian procedures. The bias-mitigating procedures are based on modifications of the key step that facilitates Bayesian estimation of the censored regression model; are easy to implement; work well in both small and large samples; and lead to significantly improved inference in the censored regression model. These findings are important in light of the widespread use of the zero-censored Tobit regression and we investigate their consequences using data on milk-market participation in the Ethiopian highlands. (C) 2004 Elsevier B.V. All rights reserved.

Tobit estiamtion with unknown point of censoring with an application to milk market participation in the Ethiopian highlands

Data augmentation is a powerful technique for estimating models with latent or missing data, but applications in agricultural economics have thus far been few. This paper showcases the technique in an application to data on milk market participation in the Ethiopian highlands. There, a key impediment to economic development is an apparently low rate of market participation. Consequently, economic interest centers on the “locations” of nonparticipants in relation to the market and their “reservation values” across covariates. These quantities are of policy interest because they provide measures of the additional inputs necessary in order for nonparticipants to enter the market. One quantity of primary interest is the minimum amount of surplus milk (the “minimum efficient scale of operations”) that the household must acquire before market participation becomes feasible. We estimate this quantity through routine application of data augmentation and Gibbs sampling applied to a random-censored Tobit regression. Incorporating random censoring affects markedly the marketable-surplus requirements of the household, but only slightly the covariates requirements estimates and, generally, leads to more plausible policy estimates than the estimates obtained from the zero-censored formulation

Estimating remittance functions for Pacific island migrants

There is concern that Pacific island economies dependent on remittances of migrants will endure foreign exchange shortages and declining Living standards as remittance levels drop due to lower migration rates and the belief that migrants' willingness to remit decreases over time. The empirical validity of the remittance-decay hypothesis has never been tested. From survey data on Tongan and Western Samoan migrants in Sydney, this paper estimates remittance functions using Tobit regression analysis. It is found that the remittance-decay hypothesis has no empirical validity and migrants are motivated by factors other than altruistic family support, including asset accumulation and investment back home. (C) 1997 Elsevier Science Ltd.

Factors affecting hospital admission and recovery stay duration of in-patient motor victims in Spain

Hospital expenses are a major cost driver of healthcare systems in Europe, with motor injuries being the leading mechanism of hospitalizations. This paper investigates the injury characteristics which explain the hospitalization of victims of traffic accidents that took place in Spain. Using a motor insurance database with 16.081 observations a generalized Tobit regression model is applied to analyse the factors that influence both the likelihood of being admitted to hospital after a motor collision and the length of hospital stay in the event of admission. The consistency of Tobit estimates relies on the normality of perturbation terms. Here a semi-parametric regression model was fitted to test the consistency of estimates, concluding that a normal distribution of errors cannot be rejected. Among other results, it was found that older men with fractures and injuries located in the head and lower torso are more likely to be hospitalized after the collision, and that they also have a longer expected length of hospital recovery stay.

Bayesian estimation of the double hurdle model in the presence of fixed costs

We present a model of market participation in which the presence of non-negligible fixed costs leads to random censoring of the traditional double-hurdle model. Fixed costs arise when household resources must be devoted a priori to the decision to participate in the market. These costs, usually of time, are manifested in non-negligible minimum-efficient supplies and supply correspondence that requires modification of the traditional Tobit regression. The costs also complicate econometric estimation of household behavior. These complications are overcome by application of the Gibbs sampler. The algorithm thus derived provides robust estimates of the fixed-costs, double-hurdle model. The model and procedures are demonstrated in an application to milk market participation in the Ethiopian highlands.

A Fruticultura Irrigada de pequenos produtores no Baixo-Açu: Uma análise da eficiência de custo

This work has as an objective analyze the efficiency of producers costs of the irrigation Project Baixo-Açu , and identify the determining factors of this efficiency. To achieve these targets it was estimated, in a first stage, a frontier of costs by the method, non parametric of Data Envelopment Analysis-DEA, and measured the stakes of efficiency producers. On the second stage, it was utilized the Tobit regression pattern, estimating an inefficiency function of costs, and were indentified the associated factors of resources waste. Among the results found it was noticed the existence of a high waste of resources, that represent more than 54% of effective cost. Among the factors with the highest wastes are: energy, herbicides, defensives and chemical fertilizers. In a general way, the producers presented low efficiency level and, only, two, of seventy-five researched, achieved the frontier of costs minimization. These results reveal, in a certain way, that the producers in irrigated fruit growing in the project Baixo-Açu don t seek to minimize the production costs. It was still noticed, that the reduction of resources waste, and this way the inefficiency of costs, is associated with the agriculturalist education, his experience in agriculture, his access to the technical assistance and credit

A eficiência do gasto e da qualidade da saúde pública: uma análise nos municípios do estado do Rio Grande do Norte (2004 e 2008)

The overall objective of this study is to analyze the efficiency in the use of resources and the quality of public health in the municipalities of Rio Grande do Norte, from 2004 to 2008. It also seeks to identify the determinants of municipal inefficiency and measure the productivity of public spending on health. To this end, three methods of analysis are used: the DEA, the Malmquist index and the Tobit regression model. Among other findings, it appears that municipalities considered more inefficient in the measurement of expenditure on health make the largest expense in this function. On the other hand, from 2004 to 2008, only 13 municipalities showed an increase in the productivity of public spending. It is also noted that municipalities considered efficient in quality of health, although having more physical and human resources, offer fewer health services to the population. In all, the major determinants of health spending inefficiencies are the variables: age of the mayor, coalition, population density, literacy race and budget revenues. Regarding the inefficiency of the health quality, variables such as: coalition, literacy race have strong influence on this behavior. Thereby, the hypotheses proposed by the study have been fully accepted. In other words, for the efficiency of the quality and health spending it is needed more than resources, i.e., the expenditure shows itself as essential, but not enough, for political and economic aspects also interfere with the performance of spent and in the quality of health care offered to the population

Dimensional correlates of poor insight in obsessive-compulsive disorder

Background: Cross-sectional studies have associated poor insight in patients with obsessive-compulsive disorder (OCD) with increased OCD symptom severity, earlier age of onset, comorbid depression, and treatment response. The goal of this current study was to examine the relationship between dimensions of OCD symptomatology and insight in a large clinical cohort of Brazilian patients with OCD. We hypothesized that poor insight would be associated with total symptom severity as well as with hoarding symptoms severity, specifically. Methods: 824 outpatients underwent a detailed clinical assessment for OCD, including the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), the Dimensional Yale-Brown Obsessive-Compulsive Scale (DY-BOCS), the Brown Assessment of Beliefs Scale (BABS), a socio-demographic questionnaire, and the Structured Clinical Interview for axis I DSM-IV disorders (SCID-P). Tobit regression models were used to examine the association between level of insight and clinical variables of interest. Results: Increased severity of current and worst-ever hoarding symptoms and higher rate of unemployment were associated with poor insight in OCD after controlling for current OCD severity, age and gender. Poor insight was also correlated with increased severity of current OCD symptoms. Conclusion: Hoarding and overall OCD severity were significantly but weakly associated with level of insight in OCD patients. Further studies should examine insight as a moderator and mediator of treatment response in OCD in both behavioral therapy and pharmacological trials. Behavioral techniques aimed at enhancing insight may be potentially beneficial in OCD, especially among patients with hoarding. © 2011.

Technical Efficiency of State Owned Enterprises in China (1980-1989): An Assessment of the Economic Reforms

This paper uses Data Envelopment Analysis to examine changes in levels of technical efficiency over time in China's state-owned enterprises (SOEs) during 1980-1989. Our paper adds to the growing body of literature in this area by obtaining measures of technical efficiency of individual SOEs over years and by identifying how different aspects of the reforms have affected efficiency. We estimate a Tobit regression model, using the technical efficiency score as the dependent variable and a set of reform variables and firm attributes as regressors. We find that specific aspects of the reforms were very effective in improving technical efficiency.

Eficiencia en la distribución: una aplicación en el sector de agencias de viajes

El objetivo de este trabajo consiste en estimar la eficiencia productiva y de escala con la que operan los intermediarios del sector minorista español de distribución turístico. Adicionalmente, se pretende examinar los determinantes de la eficiencia en términos de la integración vertical, concentración horizontal, tamaño y resultados de las entidades. La metodología aplicada se apoya en diversas técnicas de medición de eficiencia (paramétrica de naturaleza estocástica y no paramétrica del Análisis Envolvente de Datos, DEA), así como en modelos tobit para conocer el impacto de los factores del mercado y de la empresa sobre los niveles de eficiencia. La aplicación empírica realizada en una muestra de 50 agencias de viaje de nuestro país evidencia, por un lado, unos elevados índices de ineficiencia técnica y de escala, destacando en el último caso los rendimientos decrecientes; y por otro, que el tamaño y el ROA son los factores determinante de la eficiencia de escala, mientras que la concentración del mercado explica la eficiencia técnica.

Spesa pubblica in Sanità, Istruzione e Ricerca: efficienza, efficacia e determinanti

La ricerca intende analizzare l’efficacia della spesa pubblica, l’efficienza e le loro determinanti nei settori della Sanità, dell’Istruzione e della Ricerca per 33 paesi dell’area OCSE. L’analisi ha un duplice obiettivo: da un lato un confronto cross country e dall’altro un confronto temporale, prendendo in considerazione il periodo che va dal 1992 al 2011. Il tema della valutazione dell’efficacia e dell’efficienza della spesa pubblica è molto attuale, soprattutto in Europa, sia perché essa incide di quasi il 50% sul PIL, sia a causa della crisi finanziaria del 2008 che ha spinto i governi ad una riduzione dei bugdet e ad un loro uso più oculato. La scelta di concentrare il lavoro di analisi nei settori della Sanità, dell’Istruzione e della Ricerca e Sviluppo deriva da un lato dalla loro peculiarità di attività orientate al cliente (scuole, ospedali, tribunali) dall’altro dal ruolo strategico che essi rappresentano per lo sviluppo economico di un paese. Il lavoro è articolato in tre sezioni: 1. Rassegna dei principali strumenti metodologici utilizzati in letteratura per la misurazione della performance e dell’efficienza della spesa pubblica nei tre settori. 2. Valutazione e confronto dell’efficienza e della performance della spesa pubblica dal punto di vista sia temporale sia cross-country attraverso la costruzione di indicatori di performance e di efficienza della spesa pubblica (per approfondire l'indice dell'efficienza ho applicato la tecnica DEA "bootstrap output oriented" con indicatori di output ed input non simultanei mentre l’evoluzione dell’efficienza tra i periodi 2011-2002 e 2001-1992 è stata analizzata attraverso il calcolo dell’indice di Malmquist). 3. Analisi delle variabili esogene che influenzano l’efficienza della spesa pubblica nei settori Salute, Istruzione e Ricerca e Sviluppo attraverso una regressione Tobit avente come variabile dipendente i punteggi di efficienza DEA output oriented e come variabili esogene alcuni indicatori scelti tra quelli presenti in letteratura: l’Indicatore delle condizioni socioeconomiche delle famiglie (costruito e applicato da OCSE PISA per valutare l’impatto del background familiare nelle performance dell’apprendimento), l’Indicatore di fiducia nel sistema legislativo del paese, l’Indicatore di tutela dei diritti di proprietà, l’Indicatore delle azioni di controllo della corruzione, l’Indicatore di efficacia delle azioni di governo, l’Indicatore della qualità dei regolamenti, il PIL pro-capite. Da questo lavoro emergono risultati interessanti: non sempre alla quantità di risorse impiegate corrisponde il livello massimo di performance raggiungibile. I risultati della DEA evidenziano la media dei punteggi di efficienza corretti di 0,712 e quindi, impiegando la stessa quantità di risorse, si produrrebbe un potenziale miglioramento dell’output generato di circa il 29%. Svezia, Giappone, Finlandia e Germania risultano i paesi più efficienti, più vicini alla frontiera, mentre Slovacchia, Portogallo e Ungheria sono più distanti dalla frontiera con una misura di inefficienza di circa il 40%. Per quanto riguarda il confronto tra l’efficienza della spesa pubblica nei tre settori tra i periodi 1992-2001 e 2002-2011, l’indice di Malmquist mostra risultati interessanti: i paesi che hanno migliorato il loro livello di efficienza sono quelli dell’Est come l’Estonia, la Slovacchia, la Lituania mentre Paesi Bassi, Belgio e Stati Uniti hanno peggiorato la loro posizione. I paesi che risultano efficienti nella DEA come Finlandia, Germania e Svezia sono rimasti sostanzialmente fermi con un indice di Malmquist vicino al valore uno. In conclusione, i risultati della Tobit contengono indicazioni importanti per orientare le scelte dei Governi. Dall’analisi effettuata emerge che la fiducia nelle leggi, la lotta di contrasto alla corruzione, l’efficacia del governo, la tutela dei diritti di proprietà, le condizioni socioeconomiche delle famiglie degli studenti OECD PISA, influenzano positivamente l’efficienza della spesa pubblica nei tre settori indagati. Oltre alla spending review, per aumentare l’efficienza e migliorare la performance della spesa pubblica nei tre settori, è indispensabile per gli Stati la capacità di realizzare delle riforme che siano in grado di garantire il corretto funzionamento delle istituzioni.

The impact of ICT on productivity of airline industry

Airline industry is at the forefront of many technological developments and is often a pioneer in adopting such innovations in a large scale. It needs to improve its efficiency as the current trends for input prices and competitive pressures show that any airline will face increasingly challenging market conditions. This paper has focused on the relationship between ICT investments and efficiency in the airline industry and employed a two-stage analytical investigation, DEA, SFA and the Tobit regression model. In this study, we first estimate the productivity of the airline industry using a balanced panel of 17 airlines over the period 1999–2004 by the Data Envelop Analysis (DEA) and the Stochastic Frontier Analysis (SFA) methods. We then evaluate the impacts of the determinants of productivity in the industry concentrating on ICT. The results suggest that regardless of all the negative shocks to the airline industry during the sample period, ICT had a positive effect on productivity during 1999-2004.

Economic efficiency of smallholder maize producers in Western Kenya:a DEA meta-frontier analysis

Maize is the main staple food for most Kenyan households, and it predominates where smallholder, as well as large-scale, farming takes place. In the sugarcane growing areas of Western Kenya, there is pressure on farmers on whether to grow food crops, or grow sugarcane, which is the main cash crop. Further, with small and diminishing land sizes, the question of productivity and efficiency, both for cash and food crops is of great importance. This paper, therefore, uses a two-step estimation technique (DEA meta-frontier and Tobit Regression) to highlight the inefficiencies in maize cultivation, and their causes in Western Kenya.