I suspect the volume of "motivational" posts far out-pass all the posts combined and I am certain you would see that data in your own records around the 3rd week of each January - which is when most people start falling back into old, previous patterns. You have that data. Do you know why, that data repeats itself, year after year? ( lack of _____ )
Your own data would certainly show that there is a huge increase in people wanting to follow their fitness goals - probably mid December onwards - and they do great and they make wonderful progress but so many (as your data shows) fall by the side and gradually [they] end up back where they were in the beginning. I am certain that your data would show that there is a huge decrease in members, continuing afterwards. This makes sense, not only in Johnstone Fitness but in other forums as well.
I believe, by creating such a forum you could create a "buddy" system for newbies that clearly addresses the "motivational" factor(s). You could even pair up senior members via email with new members that are trying to maintain their fitness goals. Talk to the wife and see what she thinks. Talk to others too. There must be a great way that this can be incorporated into your site and the timing is perfect. Perhpas, more can be done!?!
Does it really(genuinely) matter what 'your' volumes are? I am not seeking t-shirts here, myself..... Perhaps that coveted ball-point pen!?
If you can keep one person attached to their fitness goals.... well, that is, in my opinion, worth it.
“Successful people ask better questions, and as a result, they get better answers.” – Tony Robbins