Based on the context and the answer, generate a question. 

Context: In the US , the number one hit on my birthday was " With Or Without You " by U2 , which is rather cool because it 's quite possibly my favourite U2 song .

Answer:

That the number one hit at any given time is most likely not the same in every part of the world .



What can be inferred about song rankings from the author 's specification of where the U2 song was the number one hit at the time ?