For an idea of how many ARMs are in SD compared to the rest of the country, go to http://www.fhfb.gov/Default.aspx?Page=53 and look at 5. Quarterly by Metropolitan Area. This only reports from 4th 1/4 2006 to 4th 1/4 2007 but I think I might have data from previous 1/4’s saved on my computer I can post tomorrow hopefully.