This chapter demonstrates that indicators and measurement tools are often fuzzy. It is a call for more and better city data and a more careful use of statistics. The chapter briefly reviews the Habitat Commitment Index (HCI), its methodology and data collection process. It focuses on city performance in four HCI indicators and examines city-level trends in inequality and greenhouse gas emissions. The chapter returns to the question of urban data and implications for future global city-level analyses. The HCI offers an alternative approach, as it assesses performance in light of local capacity. Unlike the country-level HCI, the city-level HCI could not rank cities by their performance in fulfilling global targets. The chapter offers a glimpse of an immense work that lies ahead, in harmonizing and growing local databases.