I mentioned in an earlier post a project I am working on, where I try to use my knowledge in statistics to best estimate the number of BJJ white belts practicing at BJJ academies around the UK (at least once per week).
Once I know the number of BJJ white belts in the UK, I can add that to the registered BJJ blue belts, BJJ purple belts, BJJ brown belts and of course BJJ black belts. The result is the estimated answer to the question posed by my friend Seymour "Meerkatsu" Yang:
How many people practice Brazilian Jiu Jitsu (BJJ) in the UK?
Doing statistical analysis in anything BJJ is a mathematician's hell!
Getting information from people is like extracting deeply guarded secret submission details! If you read my previous post, you will know that I received 28 (now 29, thank you Meg!) responses from 122 emails.
I used that information to find the ratio between the number of BJJ purple belts and BJJ white belts who train at least one session of BJJ per week. I also tested the ratio between the number of BJJ blue belts and BJJ white belts at these clubs so I can get two values (and also because not all clubs have a resident BJJ purple belt).
There were a couple of clubs that were outside the margins defined by the majority of the sample, which is to be expected. I decided that these were outlier values.
With my new ratios (which I will reveal soon) the next step was to filter that less-than-perfectly-maintained list of blue, purple, brown and black belts on EFN (see link above). The reason for this was to avoid, best as I can, duplicates (i.e. brown belts whose name was never removed from the purple belt list...etc.).
Now I have, to the best of my ability and the data supplied by the UK BJJ community, the cleaned up number of BJJ blue, purple, brown and black belts in the UK plus two estimates for the number of BJJ white belts who practice BJJ at least once per week. I will gratefully publish the names of the academies that took part in this study and reveal my total figures and estimates in a future post but for now I can tell you that:
The average number of white belts to purple belts in any randomly selected BJJ academy in the UK is: 5 (6 if you exclude the outliers)
The average number of white belts to blue belts in any randomly selected BJJ academy in the UK is: 2 (3 if you exclude the outliers)
What this means is that most academies which have 1 BJJ purple belt will have total membership of approximately 9 (8.5 - 9 to be exact) students who attend at least one BJJ session per week
Here is a quick table relating BJJ Membership to Number of BJJ Purple Belts training:
|Number of Purple Belts||Total of BJJ students who attend at least one BJJ session per week|
|2||17 - 18|
|3||26 - 27|
|4||34 - 36|
|5||43 - 45|
|6||51 - 54|
Where does your* BJJ academy or BJJ gym fit in and how does it compare**?
Stay tuned for my final post on the matter, where I reveal ALL! :)
*If you academy has BJJ brown and black belts, then it doesn't fit directly into this formula. You will have to wait until the next post to see the full chart :). God Bless Meerkatsu and his Wicked Mind!
**Thanks to a comment on Facebook by Mr Shane Chittenden, I would like to explain how the table works:
I am suggesting that if an academy was chosen at random and it had, say, 4 purple belts, then it will most likely have 34 - 36 people who do BJJ at least once per week. Thanks Shane for bringing the potential confusion to my attention.
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