The results of the 6th edition of the Happy City Index were officially announced in London, at the seat of the British Parliament. The ceremony closed the largest community-driven study of urban development in the world, and was made possible through the support of Dr Rosena Allin-Khan MP, a long-standing advocate of sustainable urban development focused on residents' happiness and well-being.

This year's edition covers 251 cities and is built on 64 indicators across six dimensions: Citizens, Governance, Environment, Economy, Health and Mobility. Over five months, 466 researchers collected and validated around 150,000 data records using one shared methodology.

The Index does not try to crown a single "best city in the world". It looks for cities that combine good governance, sustainability, resilience and quality of life, and gives a more balanced picture of how they are developing.

Alongside the results, the initiative launched the Happy City Alliance, a programme to follow cities' progress over time and share what works.