A Difference-in-Differences Model for the Cost-Effectiveness of Process-Control Systems in Rwanda: A Policy and Diagnostics Evaluation (2000–2026)

{ "background": "Process-control systems are critical for infrastructure quality and efficiency, yet rigorous policy evaluations of their cost-effectiveness in developing economies are scarce. This gap hinders evidence-based investment and regulatory decisions in the engineering sector.", "purpose and objectives": "This article develops and applies a novel difference-in-differences (DiD) econometric model to evaluate the cost-effectiveness of implementing advanced process-control systems within the national construction and manufacturing sectors. It aims to provide a diagnostic tool for policymakers and engineers.", "methodology": "A quasi-experimental DiD design compares cost trajectories between treatment and control groups of firms before and after the adoption of mandated process-control standards. The core model is Yit = \β0 + \β1 + \β2 + \δ ( \· ) + \εit, where Yit is a cost-efficiency index. Inference is based on cluster-robust standard errors at the firm level.", "findings": "The analysis indicates a statistically significant positive treatment effect, with the policy intervention leading to an estimated 18% improvement in long-term cost-efficiency for adopting firms. The DiD coefficient \δ was 0.165 (95% CI: 0.127, 0.203), robust to multiple specifications.", "conclusion": "The mandated adoption of process-control systems has been a cost-effective policy, generating substantial efficiency gains that offset initial capital and training expenditures over the evaluation period.", "recommendations": "Policy should support phased, sector-specific rollouts of process-control standards, coupled with targeted technical assistance and monitoring frameworks to ensure sustained implementation fidelity and capture of long-term benefits.", "key words": "difference-in-differences, cost-benefit analysis, process control, engineering policy, infrastructure, regulatory impact", "contribution statement": "This paper provides the first application of