Search results

Contemporary literature reveals that, to date, the poultry livestock sector has not received sufficient research attention. This particular industry suffers from unstructured supply chain practices, lack of awareness of the implications of the sustainability concept and failure to recycle poultry wastes. The current research thus attempts to develop an integrated supply chain model in the context of poultry industry in Bangladesh. The study considers both sustainability and supply chain issues in order to incorporate them in the poultry supply chain. By placing the forward and reverse supply chains in a single framework, existing problems can be resolved to gain economic, social and environmental benefits, which will be more sustainable than the present practices.

The theoretical underpinning of this research is ‘sustainability’ and the ‘supply chain processes’ in order to examine possible improvements in the poultry production process along with waste management. The research adopts the positivist paradigm and ‘design science’ methods with the support of system dynamics (SD) and the case study methods. Initially, a mental model is developed followed by the causal loop diagram based on in-depth interviews, focus group discussions and observation techniques. The causal model helps to understand the linkages between the associated variables for each issue. Finally, the causal loop diagram is transformed into a stock and flow (quantitative) model, which is a prerequisite for SD-based simulation modelling. A decision support system (DSS) is then developed to analyse the complex decision-making process along the supply chains.

The findings reveal that integration of the supply chain can bring economic, social and environmental sustainability along with a structured production process. It is also observed that the poultry industry can apply the model outcomes in the real-life practices with minor adjustments. This present research has both theoretical and practical implications. The proposed model’s unique characteristics in mitigating the existing problems are supported by the sustainability and supply chain theories. As for practical implications, the poultry industry in Bangladesh can follow the proposed supply chain structure (as par the research model) and test various policies via simulation prior to its application. Positive outcomes of the simulation study may provide enough confidence to implement the desired changes within the industry and their supply chain networks.

This paper aims to propose an alternate, efficient and scalable modeling framework to simulate large-scale bike-sharing systems using discrete-event simulation. This study uses this model to evaluate several initial bike inventory policies inspired by the operation of the bike-sharing system in Mexico City, which is one of the largest around the world. The model captures the heterogeneous demand (in time and space) and this paper analyzes the trade-offs between the performance to take and return bikes. This study also includes a simulation-optimization algorithm to determine the initial inventory and present a method to deal with the bias caused by dynamic rebalancing on observed demand.

This paper is based on the analysis of an alternate and efficient discrete-event simulation modeling framework. This framework captures the heterogeneity of demand and allows one to experiment with large-scale models. This study uses this model to test several initial bike inventory policies and also combined them with an optimization engine. The results, provide valuable insights not only for the particular system that motivated the study but also for the administrators of any bike-sharing system.

The findings of this paper include: most of the best policies use a ratio of bikes: docks near to 1:2; however, it is important the way they are initially allocated; a policy that contradicts the demand profile of the stations can lead to poor performance, regardless the quick and dynamic changes of bike locations during the morning period; the proposed simulation-optimization algorithm achieves the best results.

The findings are limited to the initial inventory of the system under study. The model assumes a homogeneous probability distribution function for the travel time. This assumption seems reasonable for the system under study. This paper limits the tested inventory policies to simple practical rules. There might be other sophisticated methods to obtain better solutions, but they might be system-specific.

The insights of this paper are valuable for operators of bike-sharing systems because this study focuses on the analysis of the impact of the initial inventory assuming that dynamic rebalancing may not be existing during the morning peak-time. This paper finds that initial inventory has a great impact on the performance, regardless of how quickly the bikes are dispersed across the system. This study also provides insights into the effect of dynamic rebalancing on observed demand.

Increasing knowledge about the operation of the bike-sharing system has a positive effect on society because more cities around the world could consider implementing these systems as a public transportation mode. Furthermore, delivering suggestions on how to increase the user service level could incentivize people to adopt bikes as a mobility option, which would contribute to improve their health and also reduce air pollution caused by motorized vehicles.

This paper considers that the contributions of this work to existing literature are the following: this study proposes a novel efficient and scalable simulation framework to evaluate initial bike inventory policies; the analysis presented in the paper includes an approach to deal with the bias in the observed demand caused by dynamic rebalancing and the analysis includes the value of demand information to determine an effective initial bike inventory policy.

We use simulations from a detailed dynamic computable general equilibrium (CGE) model to study three broad policies toward illegal workers in U.S. employment: supply restriction (tighter border security), demand restriction (prosecution of employers), and legalization through a guest-worker program with a visa tax. From the point of view of the welfare of legal residents, the results strongly favor the third option. In our welfare analysis, we use a six-part decomposition. This identifies effects on the occupational mix of legal employment as a major factor. Throughout the chapter, model results are explained through arguments and diagrams that will be familiar to economists, particularly those working in trade. No familiarity with the underlying CGE model is assumed. Technical details on our labor market assumptions are given in the Appendix.

This paper aims to provide a quantitative assessment of the broad economic effects of tax policy reform in the Kingdom of Saudi Arabia (KSA).

Using a dynamic computable general equilibrium (CGE) model of the KSA, three simulations are run. The first simulation is the baseline simulation, which generates growth paths of the Saudi economy in the absence of tax reform. In developing the baseline simulation, this study incorporates forecasts from the International Monetary Fund. The remaining simulations are policy simulations. A policy simulation deviates from the baseline simulation in response to a policy change. In the first policy simulation, this study introduces a value-added tax (VAT) that generates SAR 35bn. This study assumes budget neutrality with the additional tax revenue transferred to households via a lump sum payment. In the second policy simulation, this study introduces a corporate income tax that generates SAR 35bn. This study then calculates and compares the distortion these taxes introduce into the economy.

This study finds that although the introduction of new taxes increases government tax revenue, markets are distorted lowering efficiency and production. An introduction of VAT increases the cost of consumption relative to the cost of production. As a consequence, the real cost of labour increases lowering employment in the short run. Employment moves to the baseline, as wages adjust capital and real gross domestic product (GDP) is below base throughout the simulation period. The second simulation is an increase in the corporate tax rate with lowers the post-tax rates of return investors receive. This simulation shows that the negative impact on investment, capital and GDP is larger with the introduction of a corporate tax than with the VAT.

Literature focusing on tax policy reform in the Gulf Cooperation Council and, specifically, Saudi Arabia is limited. This paper contributes to the literature by focusing on the following: understanding the impact and mechanisms through which changes in taxation impact the economy more generally; understanding the potential harm caused to allocative efficiency and production due to taxes; and ways in which fiscal reform might complement other reforms such as efforts to diversify the economy, labour market and energy price reforms. This improves the information base available to policymakers charged with designing an optimal tax system that meets all future requirements of a country such as the KSA.

The authors developed and applied a CGE model for the KSA to analyse the impact of VAT and corporate tax on the Saudi economy. To the best of the authors’ knowledge, there are no recent CGE models for Saudi Arabia that have been used for tax policy or quantifying the potential harm to the economy when new taxes are introduced.

Labor markets for unskilled and low-wage workers in the United States stagnated in the last quarter of the 20th century. The collapse in the low-wage labor market has been well documented¹ and numerous research initiatives have investigated the causes. Despite some geographical mismatches between buyers and sellers low-paying jobs are generally available but forces are at work on both the demand and supply sides of unskilled labor markets that make it increasingly difficult for working families at or near the bottom of the income distribution to earn enough to meet basic needs. Welfare reform effectively increased the supply of unskilled workers, which placed added pressures on wages and earnings of low-income families.