ECONOMETRIC METHODOLOGY II : STRENGTHENING TIME SERIES ANALYSIS

This article reviews some of the recent methodology developed for the analysis of time series data stressing that the statistical properties of the individual series need to be analysed to avoid spurious regressions. A convergence of econometric methodology is entertained with specific focus on cointegration and error correction models which allows the testing of long run relationships between variables and allows for a more dynamic structure than some of the previous models that appear in the literature. An example of this is the commonly used partial adjustment model in supply analysis which is nested in the less restrictive error correction model. Tests can be performed on the validity of these restrictions. These models have a wide application in agricultural economic analysis.Research Methods/ Statistical Methods,

Modelling the demographic impact of HIV/AIDS in South Africa and the likely impact of interventions

This paper describes an approach to incorporating the impact of HIV/AIDS and the effects of HIV/AIDS prevention and treatment programmes into a cohort component projection model of the South African population. The modelled HIV-positive population is divided into clinical and treatment stages, and it is demonstrated that the age profile and morbidity profile of the HIV-positive population is changing significantly over time. HIV/AIDS is projected to have a substantial demographic impact in South Africa. Prevention programmes - social marketing, voluntary counselling and testing, prevention of mother-to-child transmission and improved treatment for sexually transmitted diseases - are unlikely to reduce AIDS mortality significantly in the short term. However, more immediate reductions in mortality can be achieved when antiretroviral treatment is introduced.antiretroviral treatment, demographic impact, HIV/AIDS prevention, simulation model, South Africa

Production Incentives for Small Scale Farmers in Zimbabwe: The Case of Cotton and Maize

The paper presents an empirical investigation of the production response of small scale producers of maize and cotton for communal agriculture in Zimbabwe. The error correction model, which employs the concept of cointegration to avoid spurious regressions, is used in the analysis. The factors affecting maize output were the price of maize relative to seed, the number of marketing depots established in the communal areas and the number of loans provided to these farmers. The factors affecting cotton output were the increase in communal lands due to the resettlement program, the number of loans extended to small scale farmers and the price of cotton relative to seed. The weather played the most significant role in determining the quantity of maize sold.Agricultural and Food Policy, Crop Production/Industries,

Estimation of the rate of return to wine grape research and technology development expenditures in South Africa

This article evaluates the impact of research and technology development in the wine grape industry in order to determine the rate of return (ROR) to these investments, and to make specific recommendations on funding. The analysis illustrates the applied and adaptive nature of the research conducted in the industry, with RORs of roughly 40 percent for R&D and extension. This is high, providing excellent motivation for increased investment in R&D.Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,

Stellar Motions in the Polar Ring Galaxy NGC 4650A

We present the first measurement of the stellar kinematics in the polar ring of NGC 4650A. There is well defined rotation, with the stars and gas rotating in the same direction, and with similar amplitude. The gaseous and stellar kinematics suggest an approximately flat rotation curve, providing further support for the hypothesis that the polar material resides in a disk rather than in a ring. The kinematics of the emission line gas at and near the center of the S0 suggests that the polar disk lacks a central hole. We have not detected evidence for two, equal mass, counterrotating stellar polar streams, as is predicted in the resonance levitation model proposed by Tremaine & Yu. A merger seems the most likely explanation for the structure and kinematics of NGC 4650A.Comment: 4 pages, accepted for publication in ApJ Letter

The Value of Value Sets

A common definition of value set will be provided and fully characterized relative to its proposed uses. We will describe, compare, and contrast several approaches to specifying and referencing value sets in a stable manner over time. The term “value set”, although ubiquitous within biomedical informatics has no common definition and has yet to be fully described in a formal manner. It is essential for the design and launch of new ontologies, biomedical informatics applications and data sharing environments that a common and well-­‐ understood definition of “value set” is provided. It is also essential that options and trade-­‐offs be understood for what type of technology is appropriate for the implementation and usage of particular types of value set for particular use cases

Estimating a Collective Household Model with Survey Data on Financial Satisfaction

We estimate a collective household model with survey data on financial satisfaction from the European Community Household Panel. Our estimates suggest that cohabitating individuals enjoy returns to scale in consumption that are towards the larger end of the range of estimates reported in the literature. They also suggest that the share of household income provided by the female partner is a significant determinant of her share of household consumption in most of the countries we study.consumption, returns to scale, collective household models

Understanding perceptions of citizen demeanour: using an experimental design to understand the impact of encounter and observer characteristics

Systematic social observations of police-citizen encounters have revealed that citizen demeanour is an important predictor of outcomes (e.g. arrests and searches). Drawing from research on stereotypes and impression formation, we examine whether characteristics of the encounter and/or observer affect how respondents perceive demeanour. We exposed undergraduates (n = 255) to a randomly rotated series of five between-subjects design, in which characteristics of the encounter (citizen race, gender, or age; officer gender; neighbourhood context) and the level of demeanour displayed were manipulated. OLS regression was used to examine how these manipulations interact to produce our dependent variable – perceptions of demeanour – and whether characteristics of the observer matter for perceptions, independent of the manipulations. We find that some aspects of the encounter, specifically officer gender and the socio-economic context of the neighbourhood, influence perceptions of demeanour. Previous victimisation, observers’ race, and perceptions of the police also impact how demeanour is perceived. These findings suggest that understanding the impact of citizen demeanour on police-citizen encounters requires consideration of encounter and observer characteristics