A cross-section analysis of household demand for food and nutrients in Tanzania

Undernutrition and malnutrition are still problems of unacceptable proportions in many developing countries. However, the debate on the roles of income and other socio-economic variables such as women’s education and household size on food and nutrient demand continues. This study examines the demand for food and nutrients amongst households in Tanzania, using recent survey data. A quadratic almost ideal demand system (QUAIDS) is employed to estimate price and expenditure elasticities, as well as the impact of socio-economic variables on food demand patterns. A moment-based instrumental variable approach is then used to analyse the determinants of nutrient demand. The results show that income and other socio-economic variables exert significant effects on the demand for food and nutrients. The estimated expenditure elasticities for the nutrients range from 0.307 for iron to 1.26 for Vitamin B₁₂. The elasticities are higher for those micronutrients that are consumed through animal products and lower for those micronutrients that are mainly obtained through staple foods. These results reflect the higher expenditure elasticities for meat, fish, eggs, milk, and milk products, as well as fruits and vegetables, relative to cereals and pulses, reinforcing the assertion that the demand for Vitamins A and B₁₂, as well as calcium and zinc will increase with rising income.     

Buyer preferences for sheep and goats in southern Nigeria: A hedonic price analysis

A survey of two rural markets in southwest Nigeria over 14 months showed that supplies, sales and prices of sheep and goats varied widely during the period with a sharp peak during the Muslim festival of' Eid-el-Kabir and a smaller peak during the Christmas-New Year period. Local West African Dwarf (WAD) sheep and goats and northern Y'ankasa sheep and Red Sokoto goats were traded in the markets and animals were purchased for rearing, trading, ceremonies, butchering/catering, sacrifice, and festivals. There were significant differences between species/breeds purchased for various purposes. A hedonic price model was fitted to determine factors influencing price. After adjustments were made for age, weight, sex, time of transaction and market, WAD sheep commanded higher prices than WAD goats and Red Sokoto goats for all purposes except for butchering/catering; Red Sokoto goats commanded similar or lower prices than WAD goats depending on the purpose for purchase; and Y'ankasa sheep, principally purchased for the Eid-el-Kabir festival, commanded marginally higher prices than WAD sheep. The market share of WAD sheep is currently small and is under competition from northern sheep and goats, so increased production of WAD sheep in the south will benefit both producers and consumers in the area. In general, the results indicate that buyers have preferences for specific breeds and species for specific purposes, so producers and sellers may benefit by targeting specific buyer categories and times of the year.     

Self-Sufficiency Versus Free Trade: The Case of Rice in Iran

The dilemma of free trade and self-sufficiency for the case of rice in Iran justifies continuous governmental intervention in this market. Among all policy instruments, import tariffs have been extensively used to achieve self-sufficiency; however, the results of this policy are quite controversial and remain as a main question for researchers and policymakers. Hence, this article examines the economic impacts of increasing import tariff policy applying a multimarket spatial price equilibrium model. The results suggest that pursuing the goal of self- sufficiency by restricting rice import would be detrimental. Social welfare as well as real and per capita income are adversely affected by increasing import tariffs both in nationwide and regional scale except for 1 region, which is characterized as the largest net exporter region in Iran. Also results show that adopting free trade policies and improving rice yield may be the well-advised strategy in the case of rice in Iran.     

农村集体建设用地空间研究进展与展望

我国农村集体建设用地空间布局混乱,而现有关于农村集体建设用地空间研究方面存在理论与方法缺陷。文章对农村集体建设用地空间格局及机制、农村集体建设用地的空间优化、城乡建设用地统一空间研究领域相关研究进展进行综述,结论为现有研究存在理论体系尚未建立、研究内容不健全、研究方法以定性描述和空间描述为主等问题。建议未来该领域研究应跳出传统土地管理相关理论,多学科交叉,探索地理学、经济学在农村集体建设用地空间研究方面的理论框架;基于空间格局—演变机制—优化配置的思路,构建农村集体建设用地空间格局演变动力模型、农村集体建设用地空间与人口/产业的相互影响模型、城乡建设用地统一空间模型,从农村集体建设用地空间格局及其演变机制、农村集体建设用地空间与人口/产业的协调机制、城乡联系机制下的农村集体建设用地空间优化3方面来开展农村集体建设用地空间研究。     

黄河流域“水资源生态保护高质量发展”空间均衡性诊断

为促进黄河流域空间均衡发展,在测算黄河流域9个省区水资源可承载水平、经济社会发展水平以及生态保护水平的基础上,分析了各省区内部水资源、生态环境和经济社会3个子系统间的耦合协调发展水平,并分别以水与经济均衡、水与生态均衡、经济与生态均衡为子目标,构建了空间均衡性诊断模型,对黄河流域相邻“省区对”进行了空间均衡性诊断,反向追踪各“省区对”空间不均衡的原因。结果显示：除宁夏、甘肃外,黄河流域其他省区内部3个子系统间均已达到初级或中级协调发展阶段;黄河流域上游和下游的相邻“省区对”分别通过了均衡性判别;宁夏、甘肃、山西和内蒙古4个省区严重影响了省区间的均衡性,抑制了黄河流域整体的空间均衡发展。     

基于空间效能的城市生态网络构建*——以亳州市为例

［目的］随着我国城镇化进程的不断加快,城市生态要素不断受到侵蚀,构建城市生态网络对城市生态系统保护和修复具有重要意义。［方法］文章基于空间效能的视角,以亳州市为研究对象,运用生态网络连接性、渗透性以及均衡性评价,从生态保护和生态修复两个层面构建城市生态网络。［结果］对“网络本体—影响区—辐射区”不同空间层次的效能进行分析,研究结果表明：在“网络本体”的连接性评价中,生态连接应将河流水系等进行贯通连接,形成城市的生态骨架,并整合破碎的生态斑点,形成规模较大的斑块。“本体—影响区”的渗透性分析表明亳州大部分绿地斑块形状呈现出规则且较为离散的状态。“本体—辐射区”的均衡性评价显示亳州河流水面及沟渠较多且均匀,但是连通性较差。［结论］因此,亳州市应构建包含4个重要生态保护点、3个主要生态修复点和三级廊道体系的生态网络,同时要维持其生态廊道的自然形态,处理好现状保护与建设的关系等方面内容。     

Including Imperfect Competition in Spatial Equilibrium Models

Following Martin's paper on quadratic spatial equilibrium models this paper presents ways to incorporate imperfect competition in these models by altering the objective function of the quadratic program. This paper shows how the standard Cournot and Slackelberg equilibria may be modelled. The paper also describes the new theoretical models of consistent conjectural variations and how they may be translated into quadratic spatial equilibrium models. Situations that are likely to be modelled are discussed and appropriate models are presented. More complicated equilibria that cannot be modelled by simple adjustment of the quadratic objective function are also discussed.
Aprés la composition de Martin sur les modeles de L'équilibre quadratique et spatial, nous presentons des moyens d'incorprer la compétition imparfaite dans ces modeles en modifiant la fonction objective du programe quadratique. Nous montrons comment on peut modeler les équilibres Cournot et Stackelberg. Nous décrivons aussi les nouveaux modeles théoriques des variations consistentes et conjecturales, et comment ils peuvent éytre traduits en modeles de l'équilibre quadratique et spatial. Nous discutons les situations qui peuvent probablement étre modelées et nous presentons des modeles qui nous semblent appropriés. Nous discutons aussi des équilibres plus compliqués qui ne peuvent pas étre modelés par un simple ajustement de la fonction objective et quadratique.