If possible, it might be interesting to compare the data for Arizona with neighboring states. Apparently Arizona does not observe daylight savings time.

While the conclusions from such a comparison may not necessarily apply to more northern states, it would give an additional point of reference. (It's a pity they don't have data for Indiana in 2005, which only went to daylight savings time in 2006...)

http://en.wikipedia.org/wiki/Time_in_the_United_States#Dayli...