Well, exponential could mean "growing really fast" since that's a vague concept that doesn't really mean anything. I will concede though that I'm referring to

Well, exponential could mean "growing really fast" since that's a vague concept that doesn't really mean anything. I will concede though that I'm referring to growth at a fast pace, since that is the topic of the OP. No doubt some of the items I listed could be improving at a very low magnitude exponential rate and it is a more complicated task to provide evidence that this isn't the case.