again ,from my own experience, with each meeting I attended in my early years in, I was surprised to discover how expansion/attendance came from horizontal connections rather than new ones from outside, as someone has said earlier, families bring in extended family members and aunts/uncle etc etc.
Rarely did I ever see freshers come in from the world, it was usually through family connections, even if such connections were only tenuous or temporary in attendance.(curiosity no doubt). Thankfully none of my family did come in, something which made my exit almost painless....although I did miss some genuinely nice people.