[brianl703]

Over those years, there has been a population shift from the northeast and north central regions to the south and the west regions.

[bourbon]

Over those years, there has been a population shift from the northeast and north central regions to the south and the west regions.

True, and a good point. However, I would say it is doubtful that this migration would have any significant effect on geographic differences in military recruitment and participation. I think a claim of its significance, much less its determinative effect, would be very hard to prove.

BTW, in case you were wondering, the reason the graph starts in 1973 is b/c that is when the peacetime draft was abolished. That date is a natural starting point for any discussion about military recruitment.