The efficiency of small and medium enterprises in informal metal manufacturing in Zimbabwe: Implications for stakeholders in the agricultural sector

This study uses the structure–conduct–performance framework to examine the structure and efficiency of small and medium enterprises in the informal metal manufacturing sector in Zimbabwe. Small and medium enterprises provide a lifeline to the country's resource-poor farmers, whose numbers increased exponentially after the agrarian reform in 2000. The study utilises nationally representative, enterprise-level data from five major towns (Harare, Chitungwiza, Bulawayo, Mutare and Rusape) in Zimbabwe. Various performance measures are applied at the industry level to assess efficiency, profitability and competitiveness; these include the Herfindahl–Hirschman index, concentration ratios, average yearly profits and Tobin's q ratio. The results indicate that small and medium enterprises in Zimbabwe are modestly efficient, profitable and competitive. These findings highlight the need to integrate informal metal fabrication activities into Zimbabwe's national economic development plans.     

Truthful germs are contagious: A local-to-global characterization of truthfulness

We study the question of which social choice functions from an abstract type space to a set of outcomes are truthful, i.e., implementable by truthful mechanisms, when utilities are quasi-linear. For convex domains, our main theorem characterizes truthful social choice functions as those satisfying two properties: local weak monotonicity and vortex-freeness. The first of these constrains the function values at any two sufficiently proximal points, while the second asserts that its line integrals around sufficiently small triangular loops must vanish.The characterization implies a local-to-global principle that allows one to deduce truthfulness of a function from its behavior on arbitrarily small neighborhoods of each point. Other consequences include a simple alternate derivation of the Saks–Yu Theorem that weak monotonicity characterizes truthfulness of functions having a convex domain and finite range, and a sufficient condition for constructing truthful functions by “stitching together” truthful subfunctions on different subsets of the domain.     

The need for an alternative to shareholder value creation? The Ethomed student experience

This article aims to highlight the need for a radical break with the methodological individualism that dominates the fields of economics and management, especially finance. It advocates the need to try to understand the issues and methods that are required to coordinate economic action in order to meet social needs.The article questions methodological individualism and the dominant role played by shareholders. Is it possible to promote social welfare simply by considering it to be a result of a shareholder value maximization point of view? If not, this implies not only understanding fully the challenges that we face but also being innovative regarding the way in which we coordinate the actions that are necessary to meet these challenges head on, and perhaps promoting another character as a substitute for the shareholder.     

Firm heterogeneity and immigrant wage assimilation

This article investigates the role of job mobility in immigrant wage assimilation. I use longitudinal linked employer–employee data for Portugal to estimate the immigrant wage catch-up in log wage regressions with both individual and firm fixed effects. I show that moving to firms with higher wage premiums accounts for approximately 30% of the immigrant wage catch-up in the first years.     

Random regret minimization for consumer choice modeling: Assessment of empirical evidence

This paper introduces to the field of marketing a regret-based discrete choice model for the analysis of multi-attribute consumer choices from multinomial choice sets. This random regret minimization (RRM) model, which has recently been introduced in the field of transport, forms a regret-based counterpart of the canonical random utility maximization (RUM) paradigm. This paper assesses empirical results based on 43 comparisons reported in peer-reviewed journal articles and book chapters, with the aim of finding out to what extent, when, and how RRM can form a viable addition to the consumer choice modeler's toolkit. The paper shows that RRM and hybrid RRM–RUM models outperform RUM counterparts in a majority of cases, in terms of model fit and predictive ability. Although differences in performance are quite small, the two paradigms often result in markedly different managerial implications due to considerable differences in, for example, market share forecasts.     

Sustainable hub location under mixed uncertainty

This paper addresses a novel sustainable hub location problem (SHLP) in which two new environmental-based cost functions accounting for air and noise pollution of vehicles are incorporated. To cope with uncertain data incorporated in the model, a mixed possibilistic–stochastic programming approach is proposed to construct the crisp counterpart. A simulated annealing (SA) and an imperialist competitive algorithm (ICA) with a new solution representation are developed to solve real-sized instances whose performances are compared with a proposed lower bound. Finally, some computational experiments are provided to demonstrate the effectiveness of the proposed model and solution approaches.     

Modelling the implied volatility surface based on Shanghai 50ETF options

We develop a dynamic factor model to forecast the implied volatility surface (IVS) of Shanghai Stock Exchange 50ETF options. Based on the assumption that dynamic change in IVS is mean-reverting and Markovian, we use a state space model to capture the dynamics of IVS, and set the latent factors to be the Ornstein–Uhlenbeck processes. We obtain the optimal estimations of parameters using the Kalman filter algorithm. Empirical results show that our model performs better than the traditional IVS model in terms of fitting ability and prediction performance.     

Short-time at-the-money skew and rough fractional volatility

The Black–Scholes implied volatility skew at the money of SPX options is known to obey a power law with respect to the time to maturity. We construct a model of the underlying asset price process which is dynamically consistent to the power law. The volatility process of the model is driven by a fractional Brownian motion with Hurst parameter less than half. The fractional Brownian motion is correlated with a Brownian motion which drives the asset price process. We derive an asymptotic expansion of the implied volatility as the time to maturity tends to zero. For this purpose, we introduce a new approach to validate such an expansion, which enables us to treat more general models than in the literature. The local-stochastic volatility model is treated as well under an essentially minimal regularity condition in order to show such a standard model cannot be dynamically consistent to the power law.     

The veto mechanism in atomic differential information economies

We establish new characterizations of Walrasian expectations equilibria based on the veto mechanism in the framework of differential information economies with a complete finite measure space of agents. We show that it is enough to consider the veto power of a single coalition, consisting of the entire set of agents, to obtain the Aubin private core. Moreover, we investigate on the veto power of arbitrarily small and big coalitions, providing an extension to mixed markets of well known Schmeidler (1972) and Vind’s (1972) results in terms of Aubin private core allocations.     

Socio-economic and biophysical determinants of land degradation in Vietnam: An integrated causal analysis at the national level

Recognizing the socio-economic and biophysical causes of land degradation at the national level is important for cause-targeted strategies when designing policies for combating land degradation. This study aims to identify the biophysical and socio-economic factors that significantly affect land degradation across Vietnam and to interpret the causalities underlying the effects. The dependent variables considered in the study are spatial, the extent and intensity of degradation in three land-use zones (agriculture, forest and severely degraded abandonment). The hypothesized explanatory variables are common economic and demographic drivers and bio-physical factors such as soil, terrain constraints, and neighborhood land-use structures that are often neglected in many large-scale land degradation assessments. Instead of using a single inferential statistic technique, we used multi-linear regression and binary logistic regression in a complementary manner to increase the detectability and credibility of the degradation cause analyses. The results showed agricultural production growth had strong and consistent effects on land degradation extent and intensity. Population growth, especially in rural areas, had a strong effect on the extent of overall land degradation. The importance of a neighboring forest was revealed for its ability to reduce land degradation intensity in abandoned, unproductive lands. The concrete faceting of the causal analysis for each land-use zone as social–ecological stratum allowed us to combine the defined social–ecological contexts, contemporary theories, and hypotheses in the field to clarify the causal factors of a complex phenomenon like land degradation. The study demonstrates these contemporary inferential statistics can be complementarily used to sufficiently detect and understand land degradation causes at the national level. The results suggest implications for national land management policy: internalizing land degradation costs in the farming system evaluation for payment for ecosystem services policy, restricting forest conversion, and improving extension services and education in agrarian communities.