I would not answer this question. The hiring manager explained that they did not want to waste my time if they could not offer a better salary. I found this question irrelevant and rude. I, of course, researched the salary for open position and would not have wasted my time pursuing an interview if the salary range was not attractive to me. I understand this is a common question, but it seems as though they are just compiling data that is otherwise difficult to collect.