Nation-states are in decline anyway. In the future, it’ll be cities that influence how the world works.

This may be true, but for the time being, it’s national laws that fundamentally shape the behaviour of the seven billion people on the planet; and it’s only nations that measure and report on their behaviours in a way that can feed into a study like this. A Good City Index is being considered, but everything depends on the availability and the reliability of the data we can obtain.