Tl;dr (too long, didn't read ): this post is about an estimate of new members in the last few years, and on the total number of Scientologists EVER. For those who don't know: there's an old database around on the net which is called http://www.truthaboutscientology.com/ I have used this a lot for finding names for the big list. One way of doing that is harvesting the names from the site by way of copy/paste so I can easily check a list of names I get somewhere against completions with Excel. In June 2011 I harvested the names, and ever since I have used the list I got then. Now just Sunday I once again harvested them all again. Now let me first say there are lots of problems in the database because of spelling, women changing names through their lives because of marriages/divorces (often more times than one), and some parts of the world not being entered in the database. Let me just say there is a reason people have social security numbers. The people who entered the data, Kristi Wachter and Patty Moher being the most important contribuants AFAICT, did a stellar job though. First of course because of the sheer amount of work (thank you!), second because I'm sure the COS tried its best to get the site offline (but look, it's still there!) and third because the site tries to deal as good as possible with the limitations the data have. You can check the site out yourself. That being said I think there are some interesting preliminary conclusions possible. The first one is based on a comparison (using exact search) of the two lists I harvested. For the 2011 list I don't know anymore for what month the last completion entered was. The date of the file I have is from June 2011, so that's what I'm going at. The last completion added for the list I got Sunday was for May 2015. There are 47 months between and the 2017 list have only 3625 names that were NOT on the 2011 list. This gives me about 77 new names per month on average. Shocking, I would think. The second possible conclusion is based on the following. There are about 100k names in the trutaboutscientology database. As I said before, not all people whop were ever in are in the database. The question is how many. I am assuming that only half of the names of people who were ever in are in the database. This is based on two checks. First, I checked the big list against completions using exact comparison (vertical search in Excel). Second, I checked with a list of names from the ban aftermath petition, same method. Both gave a hit rate of about 50%. Let us now give the COS the benefit of the doubt and assume that only half or a third of the names of those who were ever in are in the database, that gives a total membership for 200k to 300k over the total COS history. No exact science here, just "guesstimating" (if that is even English, lol). Any insights welcome!