School of Business & Public Management
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Item Bank size as a mediating mechanism between financial soundness and operational efficiency: evidence from Islamic banks in sub-Saharan Africa(Emerald Publishing., 2026) Njogo, Michael Njoroge.; Dallu, Abdallah Mambo.; Korir, Fiona Jepkosgei.Purpose This study examines whether bank size mediates the relationship between financial soundness and operational efficiency of Islamic banks in sub-Saharan Africa (SSA), where the sector remains small despite growing policy relevance. Design/methodology/approach Panel data from 35 Islamic banks (2010–2024) were analysed using bias-corrected Variable Returns to Scale scores from the Simar–Wilson two-stage Data Envelopment Analysis. A panel-based mediation model with two-way fixed effects was employed, with bank size (log of deposits) as the mediator. Findings Financial soundness significantly improves operational efficiency, with asset quality exerting a negative effect and earnings stability a positive effect. However, financial soundness does not significantly influence bank size, and bank size does not significantly affect efficiency once soundness is controlled for. Consequently, the mediation hypothesis is not supported, indicating that scale does not function as a transmission mechanism in SSA Islamic banking. Research limitations/implications The findings caution against consolidation-led efficiency strategies and support policy emphasis on governance, regulatory infrastructure and operational capacity building to enhance inclusive and sustainable Islamic banking development. Originality/value This study provides one of the first empirical assessments from SSA that explicitly tests the mediating role of bank size in the soundness–efficiency relationship. The findings show that scale expansion does not operate as a transmission mechanism, suggesting that scale-driven efficiency strategies may have limited applicability.Item Capital adequacy, risk absorption, and operational efficiency of Islamic in sub-Saharan Africa(University of Turin, 2026) Njogo, Michael Njoroge.; Korir, Fiona Jepkosgei.; Dallu,Abdallah Mambo.Abstract This study examines how capital adequacy shapes the operational efficiency of Islamic banks in Sub-Saharan Africa (SSA), with particular emphasis on its role as an internal risk-absorption mechanism rather than a purely prudential stability buffer. Despite its central role in Islamic banking regulation, the efficiency implications of capital adequacy, particularly in developing and institutionally constrained Islamic finance markets, remain largely unexplored. Based on a balanced panel of fully-fledged Islamic banks in SSA from2010to 2024, the paper employs a two-step empirical approach. Bias-corrected operational efficiency scores are estimated in the first stage using the Simar–Wilson two-stage Data Envelopment Analysis (DEA) framework. In the second stage, we explore the non-linear effects of capital adequacy on efficiency using panel regression techniques, controlling for bank-specific and institutional factors. To address endogeneity, persistence, and reverse causality, a dynamic panel model is estimated using System GMM as a robustness check. The findings indicate non-linear relationship between capital adequacy and operational efficiency. Moderate capital buffers are associated with improved efficiency through higher loss absorption capacity and stabilisation of operating costs, while excessive capitalisation is accompanied by scale inefficiencies and less effective intermediation. These results indicate that Islamic banking exhibits an efficiency trade-off in capital adequacy, as prudential strength beyond an optimal level may limit productivity in resource allocation. The study makes an important contribution to Islamic banking literature by reframing capital adequacy as a channel of structural efficiency and by providing rare dynamic evidence from SSA. This raises policy implications and suggests the need for commensurate capital calibration that balances prudential resilience against operational efficiency for emerging Sharīʿah-compliant banking systems.