I would say the very activate users, who still use there Amiga or Amiga like machine on a daily bases and buy amiga products and attend user groups etc there must be around 2,000 to 3,000, world wide.
then I would say on top of that number there are around about another 2,000 to 3,000 people who still follow the amiga and maybe use just an emulator now and again and follow progress etc.
Then most likely after that they might be as many as a million computer users who still remember what Amiga was and might have an ever so slight passing interest in the Amiga
