Infrastructure and Inclusive Growth in West Africa: Dynamic Threshold Evidence with a Focus on Nigeria

At what level does infrastructure allow economic growth to translate into human development? A Nigeria-only annual threshold model is not statistically feasible because open national data provide only 24 Human Development Index observations, six poverty observations and six inequality observations over 2000–2023. We therefore estimate a Nigeria-centred dynamic threshold model in a 16-country West African panel. The composite infrastructure index is the first principal component of electricity access, internet use, basic water and sanitation; it explains 78.4% of their joint variation. The complete dynamic sample contains 338 country-year observations. Country and year fixed effects, clustered inference and a 399-replication wild-cluster threshold test are used. A candidate breakpoint occurs at 0.544 standard deviations, near the 71st percentile. Above it, the contemporaneous growth–HDI slope appears larger. However, the threshold confidence set is wide and the bootstrap test does not reject linearity (p=0.545). The data therefore does not identify a defensible infrastructure level at which growth begins to improve human development. Average GDP-per-capita growth and institutional quality are positively associated with HDI, while Nigeria’s apparent high-infrastructure differential is weaker than the regional pattern and remains exploratory because the threshold itself is unsupported. The results caution against turning a visually plausible breakpoint into a policy target. Infrastructure policy should use service reliability and distributional outcomes, not an estimated regional index cutoff, as performance criteria.