- their age when you've "lost" them.
- what "stage" were they at in their life-newly married, lots of children, "empty nester," etc.?
- what economic advantages did they have?
- what economic limitations did they have?
- who were they responsible for?
- how "easy" was it to just "pick up and move?"
- could "family problems" have impacted their decisions?
- did they move or associate with members of their extended family--either relatives by blood or marriage?
And so on. No one operates in a vacuum.