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Non-completed matches in professional women's tennis (1975-2024) : epidemiology, trends, and associated factors of walkovers and defaults
Pena, Victoria; Baiget, Ernest; Pluim, Babette M.; Casals, Marti (Sage, 2026-01)
BACKGROUND : Walkovers (WOs) and Defaults are significant occurrences in professional tennis, leading to uncompleted matches. WOs typically result from injuries, illnesses, or unforeseen circumstances, while Defaults stem from code of conduct violations. Understanding their epidemiology is essential for optimizing competition structure and injury prevention strategies. HYPOTHESES : The incidence of WOs in Women’s Tennis Association (WTA) tournaments increases over time. Both WOs and Defaults are associated with competition-related factors. STUDY DESIGN : Retrospective cohort study. LEVEL OF EVIDENCE : Level 3. METHODS : A total of 706,816 singles matches from WTA tournaments between 1975 and 2024 were analyzed. To assess the occurrence of WOs and Defaults, potential associated factors were analyzed using absolute and relative epidemiological measures. RESULTS : The overall incidence of WOs was 5.3 per 1000 matches (95% CI, 5.13-5.47), with a slight increase observed in recent years. The WTA Tour recorded the highest incidence (incidence proportion [IP], 5.62; 95% CI, 5.28-5.98). WOs were most frequent in qualifying rounds (IP, 8.09; 95% CI, 7.66-8.55), final rounds (IP, 7.22; 95% CI, 6.75-7.73), and on carpet courts (IP, 7.21; 95% CI, 6.39-8.11). Defaults were extremely rare, with an overall incidence of 0.15 per 1000 matches (95% CI, 0.12-0.18). The highest Default incidence was recorded in qualifying rounds (IP, 0.20; 95% CI, 0.14-0.28) and was most frequent on hard courts (IP, 0.17; 95% CI, 0.13-0.22). CONCLUSION : Competitive structure and playing surface play a role in the occurrence of WOs and Defaults. These findings underscore the importance of injury prevention strategies, fair play policies, and player support systems to minimize disruptions in competition. CLINICAL RELEVANCE : Understanding the epidemiology of WOs and Defaults can help inform injury prevention strategies, optimize tournament formats, and guide policy development to reduce uncompleted matches in the WTA.
A bi-level optimization framework for virtual power plants integrating electric vehicles and demand response
Ren, Zhiling; Li, Shaoming; Guo, Jia; Lin, Dong; Dong, Yun (Elsevier, 2025-12)
The increasing penetration of wind and photovoltaic (PV) generation introduces significant uncertainty and volatility to power systems. To address these challenges, this study proposes a bi-level optimization framework for virtual power plants (VPPs) that integrates electric vehicles (EVs) and demand response (DR) to enhance renewable energy utilization, reduce carbon emissions, and coordinate the economic interests between the VPP operator (OPE) and the aggregator (AGG). The upper level maximizes the OPE’s revenue through dynamic electricity pricing, while the lower level minimizes the AGG’s cost via adaptive load scheduling. Simulation results show that, compared to a baseline case without EV and DR coordination, the proposed framework reduces peak demand by 3.02%, lowers total carbon emissions by 10.13%, and decreases renewable energy curtailment by 37.5% for wind and 42.85% for PV. To further validate robustness, the model was tested under diverse weather conditions over a one-week period, achieving even greater reductions in curtailment: 51.07% for wind and 51.38% for PV. This framework provides a scalable solution for high renewable integration, enabling both economic and environmental benefits.
The gendered impacts of IMF programs and IMF-recommended tax reforms on labour market outcomes in Ghana
Kunawotor, Mark Edem; Yobo, Eric; Minlah, Michael Kaku (Emerald, 2026)
PURPOSE : This paper examines whether or not gender disparity exists in labour market outcomes during IMF austerity programs with tax conditionality. DESIGN/METHODOLOGY/APPROACH : Annual time series data on the Ghanaian economy from 1990 to 2023 is used. The empirical strategies are the autoregressive distributed lag bounds test and the two-stage least squares instrumental variable techniques. FINDINGS : The main findings indicate that the unemployment gap between women and men widens during IMF programs, especially when tax conditionality is imposed. The evidence also suggests that, besides widening the labour force participation gap, the decline in labour force participation of women is more pronounced than that of men during IMF programs. However, stronger democratic regimes can help reduce these negative effects on women’s participation. PRACTICAL IMPLICATIONS : To address Sustainable Development Goal (SDG) 5, which aims to achieve gender equality and empower women, policymakers may need to incorporate gender considerations into public policy formulation. Particularly, gender indicators must be incorporated in the performance metrics during program design. Additionally, disaggregated data on gendered labour market outcomes must be collected and analysed appropriately to inform policy. ORIGINALITY/VALUE : This paper presents a unique case for developing countries, particularly in the Ghanaian context, due to the frequency and multiplicity with which IMF bailouts are sought. Besides focusing on unemployment and labour force participation gaps as outcome variables, gendered disaggregated data and interactive regressions are also employed to enhance the depth of the analysis.
When the cross-border remittance system fails : the impact of COVID-19 regulations on the food provision and access for cross-border migrant households in north-western Zimbabwe
Thebe, Vusilizwe (Cambridge University Press, 2025-09)
Cross-border remittances from South Africa have played a central role in the food availability and well-being of migrant labour households in semi-arid Zimbabwe. However, the outbreak of the COVID-19 pandemic and containment measures introduced by both the South African and Zimbabwean governments hampered the cross-border remittance system and the movement of goods. This paper explores the food provisioning and availability impacts of the changes brought by the cocktail of policy measures on migrant sending households, and whether these households were able to find alternative food sources locally. The study highlights a precarious situation for affected households, which saw their main source of food provisioning curtailed. It argues that the situation was further aggravated by the risk associated with alternative remittance channels, and the non-availability of local alternatives for these households, which were excluded from accessing food parcels/aid by the criteria used to determine beneficiaries. The paper demonstrates the vulnerability of migrant labour households to economic and labour market changes.
Does the public value ecosystem services secured by pine savanna restoration and bobwhite management on private lands?
Nimlos, Nicole M.; Pienaar, Elizabeth Frances; Martin, James A. (Elsevier, 2026-03)
Private land stewardship in the southeastern United States is crucial to attain pine savanna restoration and conservation of the threatened northern bobwhite (Colinus virginianus). Both government and privately funded conservation efforts secure numerous ecosystem services, including groundwater recharge, scenic open spaces, and biodiversity. Yet, we have incomplete information on whether the public values these ecosystem services. From June 15th to July 19th, 2022, we administered stated preference choice experiment surveys to 770 members of the public in Alabama, Georgia, Florida, and South Carolina to ascertain if the public values ecosystem services provided by pine savanna and bobwhite conservation. We analyzed data using hybrid mixed logit models. Respondents positively valued recovery of threatened bobwhite and gopher tortoise populations and high levels of groundwater recharge and scenic open space. Respondents with higher moral obligations to prevent land use conversion (personal norms, awareness of consequences, and ascription of responsibility related to conservation) were more likely to support allocation of taxes to pine savanna restoration on private lands. Respondents' moral obligation to prevent land use conversion was positively correlated with their engagement in outdoor recreational activities. Our findings indicate that the public values pine savanna and bobwhite conservation efforts on private lands in the Southeast, and that outreach related to pine savanna restoration efforts should appeal to people's moral obligation to support conservation of biodiversity, habitat restoration, and the provision of ecosystem services. HIGHLIGHTS • We use hybrid mixed logit models to analyze preferences for pine savanna restoration. • Moral obligation to prevent land use conversion depends on political orientation. • Recreational activities and moral obligation influence support for restoration programs. • Respondents placed greatest value on bobwhite recovery and high groundwater recharge.