General Equilibrium Modeling

Reducing food wastage has been identified as a sustainable and necessary solution for food insecurity, poverty and hunger alleviation in this fast-growing world, especially in Sub-Saharan
Africa (SSA). However, food wastage abatement has sectoral trade-offs (winners and losers) and variations which need to be explored empirically to determine if this solution is worthwhile. Furthermore, despite the relevance of staples in SSA economies and their significant share in food loss, there are relatively few literature that analyses the economic impact of its reduction. Thus this study assesses and compares the economic impact of a cassava prevention policy, integrated wastage management policy and a combined policy on food security, rural-urban income distribution, economic growth, output expansion, net waste generation, trade-off between cooking and work income, food wastage footprint as well as employment in a cassava export driven Ghanaian economy using a mixed methods
approach; namely food wastage fixed price multiplier model, value chain analysis and documentary analysis.

Kiriyenko Y.A. Equilibrium Formation in the Goods’ Market in the Open Economy of Ukraine. – Manuscript.
Dissertation submitted for the Candidate degree in Economics, specialty 08.00.01 – Economic Theory and History of Economic Thought. – Ivan Franko National University of Lviv, Lviv, 2013.

En este trabajo se evalúa la existencia del efecto tamaño en los mercados bursátiles más importantes de Latinoamérica (Argentina, Brasil, Chile, Colombia, México y Perú) para el periodo de 2002 a 2012, mediante la metodología de contrastes de sección cruzada del efecto tamaño en el contexto del CAPM. Los resultados obtenidos revelan que existe un efecto invertido en algunos de los mercados de América Latina.

Availability of quality-certified water is pertinent to the production of food and pharmaceutical products. Adverse effects of manganese content of water on the corrosion of vessels and reactors necessitate that process water is scrutinized for allowable concentration levels before being applied in the production processes. In this research, optimization of the adsorption process conditions germane to the removal of manganese from biotreated palm oil mill effluent (BPOME) using zeolite 3A subsequent to a comparative adsorption with clinoptilolite was studied. A face-centered central composite design (FCCCD) of the response surface methodology (RSM) was adopted for the study. Analysis of variance (ANOVA) for response surface quadratic model revealed that the model was significant with dosage and agitation speed connoting the main significant process factors for the optimization. R2 of 0.9478 yielded by the model was in agreement with predicted R2. Langmuir and pseudo-second-order suggest the adsorption mechanism involved monolayer adsorption and cation exchanging. Water Environ. Res., 87 (2015). KEYWORDS: adsorption, equilibrium, optimization, manganese, 3A molecular sieve zeolite, isotherms, kinetics, response surface methodology, clinoptilolite.

En este artículo se utiliza un modelo dinámico estocástico de equilibrio general (DSGE) neoclásico para evaluar el impacto de choques de oferta (productividad) y demanda (comercio externo) sobre el desempeño económico. Además, se analizan decisiones de política económica, en especial, el efecto del gasto público sobre la economía según las condiciones en que éste se realice. Los ejercicios realizados muestran que con un modelo de economía abierta, una política expansiva de gasto público incrementa en el corto plazo el empleo y el producto, pero se incurre en un costo futuro adicional, que parece sugerir un impacto superior al beneficio alcanzado en el corto plazo.

ABSTRACT Progress in sensors, controllers and mechatronics devices and the development of (semi-) autonomous systems that can travel safely on uneven terrain and perform many operations has encouraged research interest in the use of robotics for agriculture and forestry in hilly and mountainous terrains. Here, the main mobile configurations that are likely to be used for robotic platforms as implement-carriers (3-wheeled, conventional/articulated 4-wheeled, tracked) were reviewed and discussed in terms of their suitability for agricultural operations and their stability. A numerical index accounting for the lateral stability of a vehicle, the roll stability index, was used to indicate the in-field working capacity of these platforms during side-slope operations. Assuming the same overall dimensions for all the configurations, the 3-wheel configuration, although very simple and agile, was seen as being the least stable, while a tracked vehicle was the most stable, although it had some important drawbacks when used in an agricultural context. This drawbacks included increased soil erosion and landslides caused by its tracks especially in the areas involving turning manoeuvres. The articulated system was found to be the most suitable for uneven and side-slope terrains because of its optimal steering capacity, agility and good stability. It was found to reach a critical stability angle close to the 4-wheel vehicle.

A methodological approach for evaluating a priori the stability of agricultural vehicles equipped with different mounted implements and operating on sloping hillsides is shown here. It uses a Matlab simulator in its first phase and, subsequently, the Response Surface Modelling (RSM) to evaluate the coefficients of a set of regression equations able to account for the Type-I and Type-II stability of the whole vehicle (tractor + implement with known dimensions and mass). The regression equations can give reliable punctual numeric estimations of the minimum value of the Roll Stability Index (RSI) and can verify the existence of a Type-I equilibrium without the need of using the simulator or knowing any detail about the model implemented in it. The same equations can also be used to generate many intuitive graphs (“equilibrium maps”) useful to verify quickly the possible overturning of the vehicle. A case-study concerning a 4-wheel drive articulated tractor is then presented to show the...

ABSTRACT Progress in sensors, controllers and mechatronics devices and the development of (semi-) autonomous systems that can travel safely on uneven terrain and perform many operations has encouraged research interest in the use of robotics for agriculture and forestry in hilly and mountainous terrains. Here, the main mobile configurations that are likely to be used for robotic platforms as implement-carriers (3-wheeled, conventional/articulated 4-wheeled, tracked) were reviewed and discussed in terms of their suitability for agricultural operations and their stability. A numerical index accounting for the lateral stability of a vehicle, the roll stability index, was used to indicate the in-field working capacity of these platforms during side-slope operations. Assuming the same overall dimensions for all the configurations, the 3-wheel configuration, although very simple and agile, was seen as being the least stable, while a tracked vehicle was the most stable, although it had some important drawbacks when used in an agricultural context. This drawbacks included increased soil erosion and landslides caused by its tracks especially in the areas involving turning manoeuvres. The articulated system was found to be the most suitable for uneven and side-slope terrains because of its optimal steering capacity, agility and good stability. It was found to reach a critical stability angle close to the 4-wheel vehicle.

The labor share in the income of Turkey is confoundingly low according to official figures. By comparison, the average labor share of OECD members is two times higher than that of Turkey. Is this because labor productivity is low, or is it because imperfect competition, which amplifies profits, is overwhelmingly high in Turkey? We estimate preferences, technology parameters, and price markup in a dynamic general equilibrium model to answer this question using GMM. To our surprise, the results suggest that the crucial factor suppressing the share of labor in Turkey is high price markup, and the role of low productivity of labor is negligible. The results are robust to the use of different instrumental variables.

Computable General Equilibrium (CGE) models are probably the most utilized tool globally for development planning and macro policy analysis. Despite this their history is not available in the literature, their theoretical grounding is never explained, and the mechanics of the models remain hidden under layers of rhetoric, myths and hand gestures at various theoretical structures. Therefore, this paper explains what CGE models are, how they work, and where they came from. It will be shown that CGE models have always been and are macroeconomic models, and not based on general equilibrium theory. In doing so, it will detail how Walras’s general equilibrium is not equivalent to Arrow-Debreu’s General Equilibrium, and that CGE models use neither of those frameworks. Furthermore, this paper gives the history of the model and identifies its (relatively) few key variables, in order to explain how model builders construct CGE models, and consciously impose causality, while
choosing exogenous variables that define results. CGE models can be a very useful policy tool, but only by understanding that it is a static fixed output model, not built for dynamic analysis along the lines of Arrow-Debreu general equilibrium. With this paper in hand, users will be able to know which questions to ask model builders, to ensure more transparency and clarity in future CGE models.

In a small open developing country context, the author considers a three-sector general equilibrium framework and tries to find out the effects of foreign capital inflow on welfare of the country. Comparative-static results show that foreign capital inflow widens the skilled-unskilled wage gap under some reasonable conditions, although it causes an expansion of the foreign enclave and the agricultural sector and contraction of the domestic manufacturing sector. Taking sector specific foreign capital, the authors find that foreign direct investment is beneficial in a free market small open economy in the absence of tariff.

We define continuous-time dynamics for exchange economies with fiat money. Traders have locally rational expectations, face a cash-in-advance constraint, and continuously adjust their short-run dominant strategy in a monetary strategic market game involving a double-auction with limit-price orders. Money has a positive value except on optimal rest-points where it becomes a “veil” and trade vanishes. Typically, there is a piecewise globally unique trade-and-price curve both in real and in nominal variables. Money is not neutral, either in the short-run or long-run and a localized version of the quantity theory of money holds in the short-run. An optimal money growth rate is derived, which enables monetary trade curves to converge towards Pareto optimal rest-points. Below this growth rate, the economy enters a (sub- optimal) liquidity trap where monetary policy is ineffective; above this threshold inflation rises. Finally, market liquidity, measured through the speed of real trades, can be linked to gains-to-trade, households’ expectations, and the quantity of circulating money.

This note argues that Rational Expectations is yet another example of the Chicago School's reliance on the Tight Prior Equilibrium, which itself is inconsistent and cannot account for time and true uncertainty.

Critical Review, 2 (2-3), Spring/Summer 1988

سیاست گذاری¬های کنترل جمعیتی دهه 1370 در ایران موجب افزایش جمعیت سالمند  در دهه های آتی خواهد شد. این پدیده اثرات اقتصادی و چالش های مالی قابل توجهی درپی خواهد داشت، بطوری که خانوارها امکان تأمین مالی حمایت لازم دوران سالمندی را نخواهند داشت. لذا این مسئله ضرورت نیاز به حمایت دوران سالمندی توسط دولت به جهت ایجاد رفاه اجتماعی بالاتر و جلوگیری از فقر سالمندان را نمایان می سازد. مقاله حاضر با استفاده از مدل نسل¬های همپوش اوئرباخ-کوتلیکوف مجموعه-ای از روند¬های اقتصادی ناشی از سالمندی جمعیت در یک دوره 300 ساله بر اساس بودجه متوازن تأمین اجتماعی شبیه سازی شده است. نیروی محرکه مدل، انتقال جمعیتی است که برونزا درنظر گرفته می¬شود و بر اساس پیش بینی های سناریوی میانی سازمان ملل نرخ رشد جمعیت تا سال 2040 از 1.2 درصد به صفر کاهش می یابد.
یافته های تحقیق نشان می دهد کاهش در نرخ رشد جمعیت به منزله کاهش در عرضه نیروی کار بوده که موجب افزایش نسبت سرمایه به نیروی کار و  منجر به کاهش هزینه استفاده از سرمایه، کاهش نرخ بهره و افزایش نرخ دستمزد می گردد. با کاهش نرخ رشد جمعیت، افراد مجبور به پرداخت حق بیمه تأمین اجتماعی بالاتر و نسل جوان بار مالیاتی بیشتری را متحمل می شوند. بنابر این تغییرات جمعیتی، اولویت های رفاهی را تهدید کرده و موجب ایجاد نابرابری بین نسلی می شود.

        کلمات کلیدی: مدل نسل های همپوش(OLG)، سالمندی جمعیت، عرضه نیروی کار

This essay develops a simple worker-capitalist model. We first show that if labor markets clear at low wages then certain produced commodities are over-supplied due to inadequate
demand. This implies that any voluntary trade between firms and consumers is Pareto inefficient. Nonetheless, this inefficiency can be rectified by a Pareto-improving income
transfer from capitalists to workers. We claim that these results point out an efficiency enhancing role for the welfare state, and demonstrate the markets’ incompetency for
coordinating economic activity efficiently, thus evoking the Marxian/Keynesian polemics. Finally, we analyze price cycles in a simple setting of Walrasian price adjustment.

Resumen: El documento presenta los elementos explicativos de la política de precios de los energé-ticos la cual se origina en los tradicionales programas de ajuste que procuran mejorar el resultado de las finanzas públicas y la cuenta corriente de la balanza de pagos. Se desarrolla una matriz insumo-producto (mip) ad hoc considerando al sector hidrocarburos, la electricidad, la industria maquiladora de exportación (ime) y el resto de actividades productivas con año base 2003. A partir del diseño e implantación de un modelo de equilibrio general poskeynesiano se evalúan los impactos de diferentes escenarios con respecto a los precios de los energéticos. Se concluye que la importancia de los impactos macroeconómicos de las modificaciones en los precios debería promover el abandono de algunas de las prácticas actuales por otras que permitan maximizar la contribución al crecimiento de los diferentes sectores productivos. Palabras clave: precios de los energéticos, efectos macroeconómicos, economía mexicana, análisis poskeynesiano.

This study presents an empirical examination of climate change related to vulnerability impacts on food security and remedial adaptation options as a suitable strategy by prioritizing needs over a 50-year period. An Empirical Dynamic Commutable General Equilibrium Model for Climate and the Economy (EDCGECE) is applied using future strategies for Malaysia against a baseline scenario of existing conditions, following the top-down options. The model takes into account various climatic variables, including climatic damage, carbon cycle, temperature and rainfall fluctuation, carbon emissions, vulnerability and carbon concentrations, which were adapted from national observational predictions of climatic changes caused by global warming from 2015 to 2065. The results prioritize climate change mitigation for the future. Specifically, this study estimates Malaysia’s food sustainability prospects without adaptation actions and with 5 % to 20 % adaptation actions overtime in different adaptation scenarios, as contrasted with the baseline. The results indicate that food sustainability cost in the baseline in 2015 is 859.3 million US Dollar (USD), which is about a 30-35 % shortage compared with the national targets, and that the shortage will rise over time to USD 987.3 million in 2065. However, the cost of applying different levels of adaptation for food sustainability over time is rising considerably. However, the residual damage also decreases with all adaptation actions in the different scenarios. Thus, adaptation shows a positive sign for Malaysia’s agricultural sectors. As growth values are positive and show rising trends, therefore the projected adaptation policy can be effective for food sustainability for sustainable future strategies in Malaysia.

The safety of agricultural tractors' drivers is a very actual topic, especially when tractors operate on side slopes, such as in terraced vineyards. This work approaches the stability problem of articulated tractors' stability by modelling, simulating and quantifying the safety of the driver with respect to both roll and pitch overturns. First of all, an articulated tractor has been modelled and simplified, after that a stability index has been defined and calculated in several simulated slope conditions when the tractor travels along a circular trajectory then, the obtained results have been compared with respect to a conventional tractor. This work is a preliminary study for a tilting test platform for real vehicles, capable to reproduce real field conditions (slope, obstacles, roughness). Finally, some directives on how exploiting the obtained results for real-time safety devices have been formulated.

Ce travail explore la dynamique de production résidentielle de la cassitérite en République Démocratique du Congo à l'aide de données mensuelles tirées du bulletin mensuel d'informations statistiques de la Banque Centrale du Congo de Mars 2016 pour la période allant de Janvier 2012 à Décembre 2015. Nous considérons un modèle auto-projectif en analyse de séries temporelles : le modèle ARIMA. L'analyse et la prévision de la production de la cassitérite se fera par la méthodologie de Box et Jenkins(1976). Abstract This work explores the dynamic residential production of cassiterite in the DRC using monthly data from the monthly bulletin of statistical information of the Central Bank of Congo in March 2016 for the period from January 2012 to December 2015. We consider a self-projective model in time series analysis : the ARIMA model. The analysis and forecasting of production of cassiterite will be through the methodology of Box and Jenkins (1976).

A methodological approach for evaluating a priori the stability of agricultural vehicles equipped with different mounted implements and operating on sloping hillsides is shown here. It uses a Matlab simulator in its first phase and, subsequently, the Response Surface Modelling (RSM) to evaluate the coefficients of a set of regression equations able to account for the Type-I and Type-II stability of the whole vehicle (tractor + implement with known dimensions and mass).
The regression equations can give reliable punctual numeric estimations of the minimum value of the Roll Stability Index (RSI) and can verify the existence of a Type-I equilibrium without the need of using the simulator or knowing any detail about the model implemented in it. The same equations can also be used to generate many intuitive graphs (“equilibrium maps”) useful to verify quickly the possible overturning of the vehicle.
A case-study concerning a 4-wheel drive articulated tractor is then presented to show the potential of the approach and how using its tools. The tractor has been studied in three scenarios, differing on where the implement has to be connected to the tractor (1: frontally; 2: frontally-laterally; 3: in the back). After performing a series of simulations, a set of polynomial models (with 6 independent variables) has been created and verified. Then, these models were used, together with the related equilibrium maps, to predict the stability of 8 implements for scenario 1, 7 implements for scenario 2, and 3 implements for scenario 3, evidencing in particular the danger of using a lateral shredder with a mass greater than 245 kg.
The proposed approach and its main outcomes (i.e., the regression equations and the equilibrium maps) can give an effective contribution to the preventive safety of the tractor driver, so it could be useful to integrate it in the homologation procedures for every agricultural vehicle and to include the resulting documentation within the tractor logbook.

In this paper, we extend the Shapley–Shubik model to a two period financial economy, and essentially address the question of the existence of an equilibrium. More precisely, we show the existence of nice equilibria, i.e. situations in which prices for both assets and commodities are strictly positive. Even if the general lines of the proof are largely influenced by the paper of Dubey and Shubik (J Econ Theory 17:1–20, 1978), most of the arguments are new because of the financial nature of the economy. It forces us to deal with a generalized Nash equilibrium, and to proscribe the use of arguments which only work with a single cash-in-advance constraint.

It is commonly believed that higher budget deficits raise interest rates. However, these crowding out effects of increasing public debt have usually been found to be small or non-existent. One explanation is that on globalised bond markets interest rate differentials are offset due to financial integration. This paper tests crowding out, and measures the degree of integration of government bond markets, using spatial modelling techniques. Our main finding is that the crowding out effect of public debt on domestic long term interest rates is small: a 1% increase in the debt ratio pushes up domestic rates by 2 pp at most. Financial integration implies an important spillover effect via international bond markets, but only between OECD, and in particular EU, countries. The feedback effect from these markets on long term interest rates is as important as the domestic crowding out effect of higher public debt. Emerging markets are not as well integrated into international capital markets,...

The safety of agricultural tractors drivers is a very actual topic, especially when tractors operate on side slopes, such as in terraced vineyards. This work approaches the stability problem of articulated tractors by modelling, simulating and quantifying the safety of the driver with respect to both roll and pitch overturns. First of all, an articulated tractor has been modelled and simplified, after that a stability index has been defined and calculatedin several simulated slope conditions when the tractor travels along a circular trajectory; then, the obtained results have beencompared with respect to a conventional tractor. This work is a preliminary studyfor a tilting test platform for real vehicles, capable to reproduce real field conditions (slope, obstacles, roughness). Finally, some directives on how exploiting the obtained results for real-time safety devices have been formulated.

We study a generalized version of Coleman (1990)’s time iteration method (GTI) for solving dynamic optimization problems. Our benchmark framework is an irreversible investment model with labor-leisure choice. The GTI algorithm is simple to implement and provides advantages in terms of speed relative to Howard (1960)’s improvement algorithm. A second application on a heterogeneous-agents incomplete-markets model further explores the performance of GTI.

The traditional mechanism of finding Nash equilibria presumes that economic actors
are capable of performing computations which even computers would take far too long
to perform. A decentralized and parallel process of interactions between simple economic
actors is presented as a more plausible micro-foundation of the concept of Nash
equilibria. It is found that agent-interactions on a scale-free network converge to an
equilibrium within reasonable time, however no convergence is found on a small-world
network, a ring and a random graph. The structure of the relations between economic
actors matters. NP computational complexity of Nash equilibria does not diminish its
empirical relevance