Interdisciplinary Sociology of Rural Market Trader Association Membership Fee Ladders and New Entrant Exclusion in Kenyan County Markets: A Regression Discontinuity Analysis of Fee Tiers

Rural market trader associations in Kenyan county markets commonly structure membership fees as graduated ladders, with each tier conferring different rights of access to stall space, credit referral and dispute resolution. Because no observational data are available, the study characterises the operating characteristics of a regression discontinuity design that would estimate the causal effect of tier assignment on new entrant participation. The analysis uses a before-after-control-impact estimator under a declared variance structure with an intraclass correlation of 0.64, between-cluster standard deviation of 6.0 and residual standard deviation of 4.5. Power was estimated across 2000 design cells for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The design achieves 80 per cent power to detect a 5 percentage point effect with 54 clusters. Fee ladders function as institutional thresholds whose exclusionary consequences are contingent on the interaction between tier structure and the distribution of new entrant resources. The contribution is a methodological framework for identifying threshold effects in associational governance, together with a sociological interpretation of how fee ladders reproduce market stratification.