Technical effi ciency of organic agriculture: a quantitative reviewThis article examines the variations in mean technical effi ciency estimates in organic agriculture and the factors that explain the observed variations. A three-stage process was employed in data collection. Firstly, journals on organic agriculture and related disciplines were identifi ed and searched. Secondly, several publishers' websites and databases, namely Cambridge Journals, Elsevier, Emerald, Oxford University Press, Sage, Taylor and Francis, and Wiley, among others, were covered. Databases included AgEcon Search, CAB Abstracts, DOAJ, EBSCOhost, Google Scholar and ScienceDirect. Thirdly, the reference lists of studies found in the fi rst and second stages were searched to identify additional literature. In all, 42 studies constituting 109 observations published in the period 2002-2014 were found. Unlike existing literature on technical effi ciency quantitative reviews in agriculture, this article employs a battery of tests to select the appropriate solution for multiple observations from the same primary study, as well as the appropriate functional form for the selected fractional regression model. The mean technical effi ciency of organic agriculture for the period of study and the effects of other study characteristics are thoroughly discussed.

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The paper examined the relationship between openness and agricultural performance using data covering the period 1995 to 2009. Representing openness as foreign direct investment (FDI) and trade openness, the results showed that there is no long run relationship between FDI and trade openness on one hand and agricultural performance on the other. In the short run, vtrade openness and FDI exerted a statistically significant negative effect on agricultural performance. Though inelastic, the sign of the coefficients showed that increased openness of Ghana's agriculture through trade and FDI do not promote performance of the sector. These results provide evidence for an examination of the type of FDI attracted into the sector. Also, the detrimental effect of trade openness suggests a re-examination of the free trade policy to provide some cushion to sections of the sector to enhance output thereby increasing performance.

The few meta-analyses published on efficiency in agriculture focused on traditional agriculture to the neglect of agribusiness. This article presents a meta-analysis on agribusiness using Ghana as a case. Databases including AgEconsearch, Google scholar, EBSCOHost, EmeraldInsight, and Wiley online Library among others were searched in order to identify published studies relating to the subsectors of agribusiness. The selected loglog fractional regression model revealed that mean technical efficiency (MTE) increased over time with a mean value of 62%. MTEs of geographical sections of Ghana are also similar. Time series models possess higher MTE than panel data MTEs. In line with theory, models without functional forms and distance functions elicited higher MTE than Cobb-Douglas and translog functions. Nontraditional agricultural production showed higher MTE than traditional agriculture. MTEs in the production subsector do not differ from those in the manufacturing subsector. While this indifference suggests that value adding manufacturing subsector is as efficient as the primary production agriculture, and the increasing MTE notwithstanding, efficiency improving measures including training in farm management are required to make up for the mean difference of 38% found. [JEL Classification: Q13]. C 2016 Wiley Periodicals, Inc.