The scope and scale of the informal food economy of South African urban residential townships: Results of a small-area micro-enterprise census

Growing urbanisation in South Africa is reflected in burgeoning Working class and informal township settlements on the fringes of its major towns and cities. Paired with this is an increasing reliance on cash as the primary means of economic transaction, which has in turn stimulated the growth of micro-enterprise business activities within the township context. This article discusses the findings of an eight-township small-area census which occurred between 2010 and 2013 in Cape Town, Johannesburg, Ekurhuleni and Durban townships representing 250 000 residents. The researchers were able to establish the scope and scale of informal food and drink retailing in these localities. Of the 10 049 micro-enterprises located in the study, some 3966 (or 39% of the total) trade in food. These include enterprises in primary production, fresh produce retailing, grocery retailing from house and spaza shops, and informal foodservice enterprises. Food is the basis for much township informal business and plays an important role in making food increasingly affordable and locally accessible, and in creating cash employment. The article builds on the knowledge base of the township informal economy role in bolstering food security needs for the marginalised.     

Estimating yield curves of the U.S. Treasury securities: An interpolation approach

Following the approach of interpolation, this paper proposes the multiple exponential decay model to fit yield curves for both the U.S. TIPS market and the conventional Treasury security market. Several estimation methods, including the unconstrained/constrained nonlinear minimization, quadratic programming, and the iterative linear least squares, are applied to estimate the unknown parameters according to different curve‐fitting purposes. Comparisons between the proposed model and the alternatives show that the multiple exponential decay successfully (1) adapts to a variety of shapes associated with yield curves, (2) (partially) keeps in line with the economic interpretations of Nelson–Siegel summarized by Diebold and Li ( 2006 ), and (3) dominates the competing models in curve‐fitting performance measured by mean fitted‐price errors over the sample period. In addition, the exact specification of a nonparametric interpolation model is pinned down by applying three statistical tools, which enable us to jointly take into account validity, optimality, and parsimoniousness of the proposed model.     

可食性小麦蛋白膜的研究

本文介绍了小麦蛋白及其成膜特性,总结了国内外可食性蛋白膜的研究现状,提出了可食性小麦蛋白膜的研究方案,并对膜的安全性及其应用作了展望。     

现代网络安全技术分析

随着网络技术的广泛应用，网络安全也越来越受到重视。本简述了网络安全问题的定义和TCP／IP协议的安全漏洞。同时，介绍了当前网络采用的安全技术。     

银行保函在业主反索赔中重要作用的探讨

我国建筑业目前正处于加入WTO后的3～5年的过渡期，国内建筑市场国际化的趋势使工程索赔问题必须与国际惯例接轨，从国际工程惯例出发，详细论述了银行保函的种类及其在业主反索赔过程中的重要作用，为业主提供了一种可以借鉴的工程项目管理方式。     

我国外汇储备：安全性、成本风险及对策

我国外汇储备狭义上的安全性，即外汇储备资产本身的安全令人担忧。我国已经为高额的外汇储备付出巨大成本和承担了很高的风险，同时，高额外汇储备也对我国经济发展产生了一系列负面影响和风险。从这个意义上来看，我国外汇储备的现状已成为威胁金融安全的一个重要隐患。因此，我国外汇储备政策的调整已经刻不容缓。     

论法律不完备性与政府介入期货市场

在期货市场上，法律不完备性问题表现得较为突出，法律对于侵害行为的阻吓作用非常有限、期货市场法律的不完备性，主要取决于期货市场的特点和性质。政府采取相关的监管方式管理期货市场非常必要，监管的介入需要满足标准化和损害（外部性）足够高的条件。政府管理期货市场立法和法院执法的作用不可或缺，但更主要的是采用监管的方式。     

经济全球化对我国投资条约缔约实践的影响

经济全球化背景下国际投资规则呈现自由化、多边化的发展态势，中国在日益激烈的吸引外资的竞争中应该积极参与区域投资条约，制定参与WT0框架下多边投资条约的战略。     

Bankruptcy laws and debt renegotiation

This paper analyzes the effect of the toughness of bankruptcy law on the number of liquidations in a simple model of borrowing and lending with asymmetric information, where the creditor cannot credibly commit to liquidate the firm if the default occurs. In our setting we consider a bankruptcy law to be a one-dimensional variable that influences creditor's expectation value of collateral. We find that there is an interval of the bankruptcy law, where the number of liquidations decreases in the toughness of the bankruptcy law. We also find that if the liquidation costs are high, softer bankruptcy law is preferred.     

Competition Policy: What are the Costs and Benefits of Measuring its Costs and Benefits?

Summary  Competition authorities are increasingly measuring the effects of their enforcement actions, seeking a robust justification for the proliferation of competition policy. We highlight the importance of identifying the right counterfactual against which to measure effects, and set out the relevant categories of costs and benefits. We then explore how a balance can be struck between the benefits and inherent limitations of these measurement exercises. Relatively crude analyses of cartel action benefits can be sufficient to achieve public legitimacy for competition policy. Assessing the effects of merger and conduct inquiries is often ambiguous, but could be used to improve decision-making processes. Director and Managing Consultant, respectively, at Oxera, Oxford and London. The valuable comments of Fod Barnes, Kerry Hughes and an anonymous referee are gratefully acknowledged. The opinions expressed in this article are those of the authors alone.