If you really count all who ever made an account then hundreds or even thousand. If you count those who posted at least once or even 100 times then no idea since I have no clue how many that are.
https://www.cdc.gov/nchs/data/nvsr/nvsr65/nvsr65_08.pdf
In USA, around 1% dies between 20 and 30. Many users registered already 5-10 years ago so that we have many deaths for sure.







