Regina vs Saskatoon

[hired_goons]

In the olden days (up to the middle 80's!) Regina was the most populous city of Sask.

Snapshot of 1981 populations: (from Wikipedia)
Regina: 162,613
S'toon: 154,210
Regina had 8k more people than S'toon back in the early 80's

Thirty years later (2011) Regina has 30k LESS people than Saskatoon.

Did S'toon annex outlying towns or some such thing?
I am curious as to what you guys think are some of the leading theories for the rise of Saskatoon relative to Regina