J. van Zyl

Bio: J. van Zyl is an academic researcher from University of Pretoria. The author has contributed to research in topics: Agriculture & Agricultural productivity. The author has an hindex of 13, co-authored 135 publications receiving 802 citations.

Breast cancer incidence and determinants of cancer stage in the Western Cape

Abstract: Objective To describe the overall and age-specific incidence rates for breast cancer and determinants of the stage of breast cancer at the time of diagnosis in the Western Cape, South Africa, Methods Data were derived from a case-control study of the association between injectable progestagen contraceptives and breast cancer conducted over a 4-year period from January 1994 to December 1997 In all, 485 cases were drawn from a study population consisting of coloured and black women under the age of 55 years, who presented with a first occurrence of invasive breast cancer at two tertiary hospitals in Cape Town A questionnaire was administered and information on a large number of variables was recorded Results The 249 cases who were interviewed during the first 2 years of the study constituted the numerator for estimates of incidence rates The overall incidence rate was 231 per 100 000 women per year The incidence rate for coloured women was 256 per 100 000, almost twice that for black women (147 per 100 000) The incidence rate in urban areas was 266 per 100 000, almost twice that in the rural areas (163 per 100 000) Stages 1 and 2 accounted for 578% of the cases Early stage at diagnosis was significantly associated with a higher educational level, membership of a medical aid, residence in an urban area and a positive family history Conclusion The data suggest that there is scope for improvement in the detection of the disease through education and access to diagnostic measures, particularly in rural and disadvantaged populations

Food Security and Structural Adjustment: Empirical Evidence on the Food Price Dilemma in Southern Africa

Abstract: This article considers effects of price on food security and the food equation in the developing areas of South Africa. Firstly, the food (or hunger) equation is examined in more detail. Secondly, thefood price dilemma is analysed using empirical data obtained elsewhere in sub‐Saharan Africa. Thirdly, the situation in the developing areas of South Africa is examined. Empirical evidence in sub‐Saharan and Southern Africa accentuates the skewness and concentration in the market participation profile of rural households with respect to especially staples. Supply response to higher prices in these areas is also limited. These findings place the food price dilemma on centre stage in Southern Africa.

A statistical analysis of the demand for maize in south africa

Abstract: In a dynamic economic situation, decisions concerning price, promotion, distribution, production and product policy must be made almost continually. Ample knowledge and information, amongst others, of various demand factors are necessary for the composition and maintenance of an efficient marketing strategy. Only then is there a thorough base for business control, strategic planning and forecasting. In this study it was endeavoured to determine some characteristics of the demand for maize in South Africa. Several important coefficients, for example price elasticity, income elasticity and cross-elasticity of the total demand for maize as well as that of individual components thereof, were calculated. These coefficients should provide useful and almost indispensable information concerning the effects of price changes, and mutual substitution and complementarity.

South African agriculture at the crossroads: an empirical analysis of efficiency, technology and productivity.

Abstract: List of Tables List of Figures Preface C.Thirtle, J.van Zyl & N.Vink Notes on the Contributors PART I Introduction to Part I C.Thirtle, J.van Zyl & N.Vink The Agrarian Structure and Empowerment: The Legacy M.Mbongwa, N.Vink & J.van Zyl Agricultural Policy: Undoing the Legacy of the Past N.Vink, J.Kirsten & J.van Zyl The Public Agricultural Research System H.Rooseboom, P.G.Pardey, H.S.von Bach & J.van Zyl PART II Introduction to Part II C.Thirtle Measuring Total Factor Productivity Growth in South African Commercial Agriculture, 1947-91 C.Thirtle, H.S.von Bach & J.van Zyl The Sources of Profitability: Relative Prices and Productivity J.van Zyl, H.van Schalkwyk & C.Thirtle Farm Size and Efficiency in South African Commercial Agriculture J.van Zyl Farm Size and Efficiency in Smallholder Agriculture J.Piesse, H.S.von Bach, C.Thirtle & J.van Zyl The Effects of the 1992 on Productivity in the Former Homelands: An Application of the Malmquist Index J.Piesse, C.Thirtle & J.van Zyl PART III Introduction to Part III C.Thirtle & R.Townsend Explaining Total Factor Productivity Growth: The Returns to Research and Extension in Commercial Agriculture C.Thirtle & J.van Zyl Cointegration and Modelling the Length and Shape of the Research Lag Y.Khatri & C.Thirtle The Effects of Policy and Technology: A Profit Function Approach Y.Khatri, C.Thirtle & J.van Zyl A Long Run Profit Function and a Review of the Returns to R C.Arnade, Y.Khatri, D.Schimmelpfennig, C.Thirtle & J.van Zyl R&D and Crop Level Supply Response in Maize, Sorghum and Wheat R.Townsend & C.Thirtle Induced Innovation, Policy and Technology: An Error Correction Model C.Thirtle, R.Townsend & J.van Zyl The Effects of Macroeconomic Policies on Agricultural Prices, Net Farm Incomes and Exports: A Vector Autoregression Approach R.Townsend & C.Thirtle A New Vision for Agriculture in South Africa J.van Zyl, C.Thirtle & N.Vink Index

Understanding farmers perceptions and adaptations to climate change and variability: The case of the Limpopo Basin farmers South Africa

Abstract: "Climate change is expected to have serious environmental, economic, and social impacts on South Africa In particular, rural farmers, whose livelihoods depend on the use of natural resources, are likely to bear the brunt of adverse impacts The extent to which these impacts are felt depends in large part on the extent of adaptation in response to climate change Adaptation is widely recognized as a vital component of any policy response to climate change Without adaptation, climate change would be detrimental to the agricultural sector, but with adaptation, vulnerability can be significantly reduced This brief is based on a study that examines farmers' perceptions of climate change and analyzes their adaptation responses to climate change and variability using household survey data from the Limpopo River Basin in South Africa" from text

Explaining Agricultural and Agrarian Policies in Developing Countries

Abstract: Political outcomes - such as agricultural taxation, subsidization, and the provision of public goods - result from political bargaining among interest groups. Such bargaining is likely to be efficiency-enhancing and growth-enhancing when equally powerful interest groups - aware of the economywide budget constraint and know the economic implications of different policy options - participate, and when impartial institutions are available to enforce decisions. The greater the deviation from these conditions, the greater the potential for efficiency-reducing outcomes, the costs of which will generally fall disproportionately on politically underrepresented or powerless groups. Material conditions of agriculture production - such as spatial dispersion, seasonal work cycles, covariance of risk, and the associated market imperfections - exacerbate the difficulties faced by small producers to engage in collective action. So, despite being generally the economically most efficient form of production, family farmers' ability to counteract the political influence of rural elites and urban dwellers is extremely limited. Lack of independent institutions and clearly defined property rights - and the presence of organizational residues - not only reduce peasants' bargaining power but may also make it more profitable for powerful groups to prefer rent seeking to productive activities. How can these undesirable outcomes be avoided, and how can sustainable policy changes be initiated? Experience indicates that fiscal crises of the state, often triggered or aggravated by an external shock, can cause lasting changes of policies and institutions. By forcing the state to devolve some of its power in exchange for financial assistance to meet its immediate needs, such a crisis can give rise to the emergence of independent legal, political, and economic institutions that are maintained even once the crisis has subsided, External actors that provide resources in terms of crisis and at the same time enhance the scope for politically least vocal parts of civil society to participate in political discourse can have a significant impact on changing policy. The paper discusses in detail the implications for research as well as for policy advice.

On the global and regional potential of renewable energy sources

Abstract: In this thesis, the central research question is: what can be the contribution of renewable energy sources to the present and future world and regional energy supply system The focus is on wind, solar PV and biomass energy (energy crops) for electricity generation For the assessment of the economic potential, we construct cost-supply curves As the economic potential also depends on the way renewables are integrated in the electricity system, we also explore the overall costs of wind electricity with increasing penetration levels of the installed wind capacity into the system The potentials of solar, wind and biomass electricity are analysed at a global and regional level, for seventeen world-regions similar as used in the IMAGE 22 model to make future use of the results for scenario analysis with the IMAGE 22 model possible The IMAGE 22 model (Integrated Model to Assess the Global Environment) is developed at the National Institute of Public Health and the Environment (RIVM)) This model is one of those used for the construction and evaluation of SRES energy scenarios by the Intergovernmental Panel on Climate Change (IPCC) In summary, we can conclude that the renewable electricity sources studied in this thesis have a potential to generate several times more electricity than the present electricity demand at costs in the range of present electricity costs Solar PV has the most significant technical potential, but is at present not available at competitive costs in grid connected options In the longer term, costs of solar PV may come down at cost levels comparable to conventional electricity, especially in sunny areas The costs depend in the case of biomass electricity strongly on the technological development of the agricultural sector, on the labour wages, the capital-labour ratio and the land rental costs Costs of wind electricity are already nearly competitive and the wind electricity sector has increased considerably the last decades However, to what extent the overall costs of wind electricity can decrease further with increasing penetration levels, depends amongst others on the available storage capacity and interconnection of the system The spatially explicit calculations done in this study provide interesting new insights concerning the potential of renewable energy sources This thesis considers on a grid-cell level, next to climatic characteristics, also characteristics of land-use and soil quality, when estimating the future potential of renewables In particular for the assessment of the future potential of biomass energy, the demand for agricultural land is of high importance as these are expected to be planted at abandoned agricultural land Land area required to generate the wind electricity potential depends on social factors, but default values in this thesis indicate that to generate 6 times the present electricity production about 11 Gha is needed, about the size of China To generate about 23 times the present electricity production with solar PV, an area of 023 Gha is needed, about 20% of China To generate biomass derived electricity equal to 5 times the present electricity production, in the A1 scenario (highest potential) at abandoned agricultural area, about 13 Gha is needed, about 120% of the area of China