Afrobarometer Round 10 as Probability-sampled Validation for the Nigerian SGT Worked Case, with Longitudinal Corroboration from Rounds 5-9

This working paper presents the first probability-sampled reconstruction of the Societrics Fundamentals layer for a Sub-Saharan African country, applied to Nigeria using Afrobarometer Round 10 data (June-July 2024, n = 1,600, margin of error ±2.5 percentage points at 95 per cent confidence). Nineteen probabilitysampled items are extracted from the Round 10 Summary of Results, harmonized to the Societrics Moderacy 1-7 scale, and aggregated via Societrics Game Theory (SGT) §4.4 domain weights to produce a weighted Fundamentals-layer reading for Nigeria in 2024. The headline result is WSI strain = 4.56 Moderacy units on the 1-7 scale, with a standard error of 0.029 and 95 per cent confidence interval [4.50, 4.61]. Longitudinal corroboration is provided by three headline indicator series extracted from Afrobarometer Rounds 5 through 9 spanning 2012 to 2022, which together with Round 10 deliver an eighteen-cell panel showing sustained deterioration in citizen assessment of country-direction, economic conditions, and living conditions, with a structural break between Rounds 8 and 9 (2020 → 2022) of magnitude 8-11 times the round-level margin of error. The Round 10 point estimate converges qualitatively with the independent stylised MVD trajectory for Nigeria 2024 (Θ = 1.20) from SGT v15 §3.9, supporting the framework's measurement consistency across institutional-index and perception-survey pathways. The paper documents Q-code drift across rounds, reports Moderacy-3-versus-Moderacy-2 anchor sensitivity (aggregate shift bounded at 0.137 units, 1.96 per cent of scale span), and identifies two specific open methodological tasks: formal calibration between the Moderacy scale and the Θ ratio, and parallel reconstruction in a second fragile-state case.