The billboard's impact is weakened by the fact that almost half of the messages are about people 'planning' to relocate outside of London. So the situation is

The billboard's impact is weakened by the fact that almost half of the messages are about people 'planning' to relocate outside of London. So the situation is bad yet they still haven't left? That kind of implies that there are still advantages to living there and they haven't outweighed the disadvantages. Why didn't the billboard creators just stick to people who have moved away? Their actions would speak louder than the words of those who may just like to moan!