Insufficient investment levels pose a challenge, notably in infrastructure, with the OECD estimating a 12% increase in fixed investment needed for sustainable growth. Megatrends like urbanization and climate change further strain public finances. Subnational governments, responsible for 57% of OECD public investment, play a crucial role. The OECD's Recommendation on Effective Public Investment offers guidance, promoting integrated strategies and intergovernmental dialogue. Despite progress, challenges persist, including limited long-term impact assessment and subnational financing options. Strengthening coordination and capacity building at all levels is essential, alongside fiscal reforms and streamlined procurement. Transparency and simplification can enhance investment effectiveness, ensuring sustainable growth and equitable development.