Evaluating a Behavioural Economics Nudge Intervention to Increase Condom Use Consistency Among Male Clients of Sex Workers in South Africa's Mining Sector: A Methodological Approach

In South Africa's mining sector, male clients of sex workers represent a high-risk group for HIV transmission, with inconsistent condom use a key driver. Behavioural economics proposes 'nudge' strategies to influence decision-making, yet robust methods to evaluate such interventions in this specific context are lacking. This methodology article describes the design of a study to evaluate a behavioural economics nudge intervention aimed at increasing condom use consistency among male clients of sex workers in mining towns. The primary objective is to present a replicable methodological framework for quantifying changes in self-reported consistent condom use. The study employs a quasi-experimental, pre-post intervention design. A sample of male clients will be recruited from mining communities in the North West Province. The intervention is a contextually tailored, loss-framed nudge delivered via illustrated pamphlets and peer discussions, emphasising the social and health losses linked to inconsistent condom use. Data on condom use consistency will be collected through structured, interviewer-administered questionnaires at baseline and follow-up. Quantitative analysis will compare pre- and post-intervention proportions, controlling for key covariates. As a methodology article, this paper presents no empirical results. The findings section details the developed methodological protocol, including the specific loss-framed messaging and the planned statistical approach for measuring effect size. The outlined methodology provides a structured, culturally adapted approach to test a low-cost behavioural nudge intervention in a hard-to-reach population. It addresses a gap in practical research frameworks for HIV prevention targeting male clients in resource-limited settings. Future applications should consider incorporating objective biological outcome measures where feasible. The framework may be adapted for other populations where sexual decision-making is influenced by heuristics and biases. behavioural economics, nudge, HIV prevention, condom use, sex work clients, mining communities, South Africa, methodology This article contributes a detailed methodological framework for evaluating behavioural nudges in HIV prevention research, specifically tailored for high-risk, hard-to-reach populations in resource-limited settings.