Cities today concentrate more than half of the world population and more than 80% of global GDP. The underlying dynamics explaining their ever increasing importance are the result of a variety of positive externalities (thicker labor markets, knowledge spillovers, input sharing…) generating self-reinforcing effects. These rapid waves of urbanization have key implications for the production of goods and services, environmental quality and human development. The world is one of density spikes and disparities, driven by the unstoppable ascendance of metropolises. Greener and more inclusive cities should be promoted in order for them to remain livable. In this respect, public policies have an important role to play
