Ipsos MORI's population is 9,000.

According to Ipsos, the answer is 27%.

Quis custodiet ipsos custodes? Who will guard the guardians?

It's not clear. Quis rogat is "Who asks?" or "Who is asking?", but without more context ipsos is hard to translate. It's a demonstrative meaning "self" or "the self-same", and in this case it's clearly the object of the verb and refers to something that is plural and masculine (or masculine + feminine). Perhaps "who asks the very same people?"