Communities go through cycles and from what I've seen the level of desirability goes in ripples outward.
For example, Whitehorn used to be not bad, then they built Castleridge and that became the "better" area, then Martindale, etc. etc.
I think two things that contribute to this is, kids getting older and home owners moving to a new area, but retaining the property as a rental.
Older areas are not immune. I live in Highland Park and I think we are just starting down the other side of the being a "hood" to becoming a "community" again.
I like this little gadget.
http://crimemap.calgarypolice.ca/con...aimerPage.aspx