The Organisation for Economic Co-operation and Development has published guidance on how Development Assistance Committee members can better use cities, regions and other subnational entities in development co-operation. It frames this as a practical response to the estimate that more than 65% of Sustainable Development Goal targets depend on local and regional governments, and says DAC members should enable subnational actors to support sustainable development in partner countries while aligning with national policies and development effectiveness standards. The guidance says DAC members should build the capacity of subnational entities, support mutual learning, and mobilise expertise and resources, while ensuring work in developing countries reflects country ownership, a focus on results, inclusive partnerships, transparency and mutual accountability. It also sets out what this looks like in practice for central governments, including policies and legal frameworks that recognise the role of cities and regions, advisory and reporting systems for official development assistance, and financial mechanisms that support local international co-operation. Examples include Spain and Italy embedding local and regional authorities in national co-ordination structures, Germany and France using dedicated reporting systems for subnational official development assistance, and France's law allowing municipalities to devote 1% of water and sanitation budgets to international co-operation, which the OECD says mobilised EUR 30 million a year 15 years after adoption. For subnational entities themselves, the OECD highlights co-ordination, transparency and participation in sustainable development monitoring, including links between planning, budgeting and evaluation. It says progress should be judged by whether decentralised development co-operation respects development effectiveness principles, mobilises context-appropriate expertise and resources, supports long-term strategies, builds peer-to-peer partnerships and mutual learning, and includes monitoring and evaluation of results and SDG impact.