Thank You Peter R! I will add this model to the toolkit when I try to explain to people why sometimes (2013) it rises 100x and sometimes (2012) hardly at all. Randomness.
Randomness is not the only possible explanation. Log-logistic adoption is another possibility for a declining rate of appreciation.
So it is not sufficient to say, "the model must be my fit, and randomness explains why the fit is off this year".
The burden of proof is on the "fit" that fits the data less (despite being more complicated), i.e. yours.
(I seriously think you are wasting your precious time, trying to argue with me about statistics. Tell me when I do likewise re: your strong point.)