They took X amount of rats in a given space with X amount of FREE FOOD every day---until ever rat was dead.....
Trained rats can not take care of them selves or control them selves---exactly demonstrating cities with their hands out for free food until they have no abilities to care for them selves.
When the free food stops for any reason---all cities will be instant cannibals 100% like the rat experiment proved.
For every new rat-----all other rats suffer.....
China pays various countries to kill their rats----often the rat killers---then eat the dead rats....again, demonstrating the future of all cities.