Diffusion of National Sustainability Policy in Saudi Higher Education: A Longitudinal Analysis of UI GreenMetric Performance Under the Saudi Green Initiative, 2010 to 2025

Saudi Vision 2030 and the Saudi Green Initiative (SGI) set national environmental targets; whether university campus operations track these has not yet been tested at system level. This study asks how national policy diffuses into measurable campus performance, using the complete Saudi UI GreenMetric record, including 88 institution-year observations across all 22 participating universities, 2010 to 2025. The quantitative, longitudinal, descriptive design combines secondary archival data, indicator normalisation, global benchmarking, and non-parametric tests, interpreted through neo institutional theory. Participation expanded from one institution to twenty-one, nearly tripling after SGI implementation began. Performance is two-tier; four institutions operate near global top 100 levels; recent entrants populate the lower half. The leading tier exceeds the top 100 mean on water (95.6 per cent) but lags furthest on energy and climate change (76.0 against 86.1). Persistent participants tend to outscore recent entrants (U = 57.0, p = 0.033), although the association between editions and score falls short of significance (rho = 0.40, p = 0.064). This study offers the first system-wide evidence that voluntary benchmarking can shift from legitimacy seeking toward capability building and derives a national reporting framework aligned with SGI targets. All findings are associations, not causal effects.