Poverty and Inequality in the First Decade of South Africa's Democracy: What Can be Learned from Panel Data?

Using a longitudinal survey of South African households over the 1993-2004 period, this paper evaluates changes in income distribution since the end of apartheid. Inequality amongst these households has markedly increased this period as initially better off households consistently improved their economic well-being. Sharp increases in measured poverty over the first half of this period were partially reversed by later improvements for some poor households. Comparisons between actual and "market-generated" income distributions suggest that these improvements were driven in part by government transfer programs. Nonetheless, the chronically poor remain a significant fraction of the total poor, and 60% of those households that were poor in 1993 are still poor in 2004. Analysis of the next generation (that is the now grown children of the original survey households) shows a similar pattern of bifurcation, with one group moving ahead rapidly, and another mired at low living levels.

Sense in Sociability? Social Exclusion and Persistent Poverty in South Africa

Social capital has been identified as an important avenue of upward mobility for poorer people. However, recent theoretical work suggests that in highly polarized societies, the accumulation of social capital is likely to be fragmented and ineffective for people at the bottom of the economic pyramid. In South Africa, apartheid-era policies created such deep, socially embedded inequality producing a self-reinforcing circle of social exclusion and persistent poverty as another of apartheid's legacies. Work to date on post-apartheid income distribution-with its demonstration of increasing inequality and poverty-is consistent with this legacy hypothesis. This paper takes this hypothesis further by using a two-pronged approach that draws on quantitative and qualitative data to explore the role of different types of assets in explaining poverty status. First, novel econometric analysis of poverty and livelihood dynamics is used to test for a poverty trap that would signal the existence of a ceiling to upward mobility for poor people. The analysis finds evidence of such a trap. Secondly, the qualitative data is used to confirm and more deeply probe the reasons behind the patterns of truncated upward mobility, finding accessibility and stability of employment and state pensions as key factors explaining why people remain poor or non-poor. While this analysis finds ample evidence of active social capital and networks, these are more helpful for non-poor households while for the poor they seem to at best help stabilize livelihood at low levels and seem to do little to promote upward mobility. This paper's confirmation of the legacy hypothesis suggests the publicly provided social safety nets that exist in South Africa need to be at least maintained if not strengthened, while state policy needs to take a more aggressive role in assuring that households have access to a minimum bundle of assets and to the markets needed to effectively build on those assets over time.

Early detection of highly transmissible viral variants using phylogenomics

As demonstrated by the SARS-CoV-2 pandemic, the emergence of novel viral strains with increased transmission rates poses a serious threat to global health. Statistical models of genome sequence evolution may provide a critical tool for early detection of these strains. Using a novel stochastic model that links transmission rates to the entire viral genome sequence, we study the utility of phylogenetic methods that use a phylogenetic tree relating viral samples versus count-based methods that use case counts of variants over time exclusively to detect increased transmission rates and identify candidate causative mutations. We find that phylogenies in particular can detect novel transmission-enhancing variants very soon after their origin and may facilitate the development of early detection systems for outbreak surveillance

INFLUENCE OF LAND TENURE ARRANGEMENTS ON GRAZING MANAGEMENT INCENTIVES

Land Economics/Use, Livestock Production/Industries,

FACTORS INFLUENCING OPTIMAL STOCKING RATES FROM A TENANT PERSPECTIVE

The terms of grazing lease contracts potentially influence the tenants incentive to preserve the vegetation resource. Annual stocking rate decisions dictate the degree of overgrazing, which can be cumulative over long periods of time. The objective of this study is to identify the impact the tenants planning horizon and cost structure specified in the lease contract has on his/her profit-maximizing stocking rate. A multi-period nonlinear programming model was developed to identify economically optimal stocking rates each year over a 24-year period. The model was solved under 1-, 4-, 8-, and 12-year leases on a per acre and per head basis. The relative importance of each lease alternative and input variable on the tenants optimal stocking rate was ranked based on standardized ordinary least squares coefficient estimates between input values and optimal stocking rates. Planning horizon and cost structure had a minor impact on optimal stocking rates relative to non-lease factors such as livestock prices and production costs. Holding other factors constant, per acre leases generated a 2% higher average stocking rate than per head leases. Optimal stocking rates were inversely related to the length of the lease. Twelve-year lease agreements generated 18 and 13% lower optimal stocking rater than the 1-year per acre and per head lease agreements, respectively. The optimal stocking rate difference between an 8-year and a 12-year lease was negligible, suggesting the 8-year lease would provide a similar incentive to protect vegetation as a lease with a longer planning horizon.Environmental Economics and Policy, Land Economics/Use,

Shear-driven size segregation of granular materials: modeling and experiment

Granular materials segregate by size under shear, and the ability to quantitatively predict the time required to achieve complete segregation is a key test of our understanding of the segregation process. In this paper, we apply the Gray-Thornton model of segregation (developed for linear shear profiles) to a granular flow with an exponential profile, and evaluate its ability to describe the observed segregation dynamics. Our experiment is conducted in an annular Couette cell with a moving lower boundary. The granular material is initially prepared in an unstable configuration with a layer of small particles above a layer of large particles. Under shear, the sample mixes and then re-segregates so that the large particles are located in the top half of the system in the final state. During this segregation process, we measure the velocity profile and use the resulting exponential fit as input parameters to the model. To make a direct comparison between the continuum model and the observed segregation dynamics, we locally map the measured height of the experimental sample (which indicates the degree of segregation) to the local packing density. We observe that the model successfully captures the presence of a fast mixing process and relatively slower re-segregation process, but the model predicts a finite re-segregation time, while in the experiment re-segregation occurs only exponentially in time

Utilizing Mucosal Protrusion Angles to Discriminate Between True and False Masses of the Small Bowel on Video Capsule Endoscopy

Background: Video capsule endoscopy (VCE) has significantly improved our ability to detect small bowel tumors. However, diagnosing small bowel tumors has remained a challenge due to their low incidence, nonspecific presentations, and the inability to use VCE to biopsy lesions identified during passage through the small bowel. To address this challenge, Girelli et al. developed a novel scoring system called the “smooth, protruding lesions index at capsule endoscopy” (SPICE) to distinguish true submucosal masses from innocent bulges1. In our study, we compared the utility of an additional morphologic criterion, the mucosal protrusion angle, with SPICE scores in detecting true submucosal masses of the small-bowel. Methods: We retrospectively reviewed the charts of 300 patients over the age of 18 who had undergone VCE for suspected small bowel lesions between the years of 2002 and 2017. In total, we analyzed the VCEs of 36 patients. SPICE scores were calculated for each patient as outlined in Girelli et al. and mucosal protrusion angles were measured using a protractor placed on the computer screen. We calculated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of both SPICE and protrusion angle. The protrusion angle was defined as the angle between the polyp and surrounding mucosa, and we hypothesized that an angle \u3e 900 suggested an external protrusion while an angle \u3c 900 suggested a submucosal mass or true polyp. Results: 25 patients had true submucosal masses (2 GIST, 6 carcinoid, 5 Peutz-Jeghers, 3 inflammatory polyps, 2 hamartomatous polyps, 1 lymphoma, 1 lipomatous polyp, 2 tubular adenomas, 1 leiomyoma, 1 cavernous hemangioma, 1 hyperplastic polyp, 1 lymphatic nodule), and 10 patients had innocent bulges due to extrinsic compression. True submucosal masses when compared to innocent bulges had an average measured angle of protrusion of 45.70 ± 20.80 vs. 108.60 ± 16.30 (p \u3c 0.0001; unpaired t-test). When compared with SPICE scores, a mucosal protrusion angle \u3c 900 had a higher sensitivity (96.0% vs. 35.0%), specificity (90.0% vs. 82.0%), PPV (96.0% vs. 82.0%) and NPV (90.0% vs. 35.0%). Acute angle of protrusion accurately discriminated between true submucosal masses and extrinsic compression bulges on Fisher’s exact test (p = 0.0001). Conclusion: Protrusion angle is a simple and useful tool for differentiating between true submucosal masses and innocent bulges of the small-bowel. Further prospective studies are needed to validate its utility in minimizing invasive interventions

Herbicide-Resistant Soybeans in Arkansas: Lessons Learned and Future Direction

In Arkansas Delta soybean production, glyphosate resistant (GR) Palmer amaranth has significantly impacted weed management. The incidence of herbicide resistant (HR) weeds has farreaching crop science, economic, and communications implications, which have been explored by the corresponding expertise of our research team members to form a comprehensive literature review. The review was used to develop policy recommendations to address current and future HR genetically modified (GM) crop use and the associated issues. The review of crop science research indicated an overall increase in herbicide application, as well as an increase in weed management programs focused around glyphosate rather than the application of multiple herbicides. The review also revealed some management methods have potential to resolve the problem, including alternating herbicide application, avoiding sub-lethal rates, using “burn down” herbicides prior to planting, crop rotation, tillage, and zero tolerance weed policies. The use of fewer herbicides rather than multiple types creates a monopolistic edge for the companies producing those few herbicides, allowing greater market control. Crisis communication methods, including developing internal readiness, conducting needs assessments, developing a relevant message, and conveying the message through appropriate channels, can be used to develop a response to the issue that will best communicate necessary information to the target audience. The team used these findings to formulate policy recommendations, which include management, economic, and communication plans that may provide a starting point to address the issue