Endogenous Technical Change, Agricultural Innovation Systems, and Productivity in Nigeria: A Theoretical and Empirical Contribution

This study develops an endogenous technical change model specific to Nigeria's agricultural innovation system and empirically tests its predictions using a novel combination of agricultural R and D investment, patent, and productivity data. Existing agricultural productivity models treat technical change as exogenous, failing to capture how research incentives, institutional arrangements, and public investment decisions endogenously determine the rate and direction of agricultural innovation. This study extends the Romer and Jones endogenous growth frameworks to the agricultural sector, incorporating the specific features of Nigeria's national agricultural research system including its public sector dominance, international research collaboration through CGIAR, and weak private sector innovation participation. The model predicts how changes in public research investment, researcher quality, international knowledge access, and innovation incentive structures affect steady-state agricultural TFP growth. Empirical testing uses a newly constructed dataset of Nigerian agricultural R and D expenditure by discipline, CGIAR technology adoption records, NAERLS variety release data, and state-level agricultural TFP estimates from 1990 to 2023. Two-stage least squares and generalised method of moments estimation address endogeneity of research investment. Findings validate core endogenous growth predictions, with research investment showing significant long-run TFP effects and international research collaboration generating the largest knowledge spillover benefits. The study contributes an original agricultural endogenous growth model for Nigeria and recommends strategic research investment prioritisation based on the estimated social returns.

Keywords: endogenous technical change, agricultural innovation, productivity, Nigeria, research investment.