price ranges, sales, credit issues?

Looking at trends in pricing over the past few years it got me to wondering about why with a 16% drop in interest rates from 2011 and a 47.1% drop from 2007, what was the makeup of the factors causing  a 3% rise in price from 2011 and a 3% rise from 2007 when size is factored in, or said another way based on size,  prices in 2007 and 2011 were identical even though interest rate environment was radically different from 2012 and in theory that differential should produce more pronounced changes in price movement. So that leads to the question how have the  price ranges performed in terms of sales.

In looking at the information below my interpretation is,  credit standards  have greatly affected the lower portion of the market and somewhat in the higher end, in buyers ability to obtain mortgages. The numbers on the charts below represent what the most probable end of the year sales number  in 2012 will look like.  First in from 2007 to 2012 from 100k to 200k the number of sales dropped by 20.75%. Then in the 200k and above the number of sales increased by 11.39%. With all things being equal, at worst case, you should see both segments of the market place increase, with probably the higher range increasing more, due to lower interest costs on the high end producing dramatically bigger dollar savings in monthly payment, caused from declines interest rate. Yet overall in Yellowstone county we see increase in average wage, number of jobs being equal and increasing population. Yet what see is the lower prices points falling in volume with essentially no change in the home being purchased by size. The higher end increasing in sales, yet not in portion to the dramatic lowering of costs. So looking forward in 2013 it presents an interesting challenge looking at a clouded crystal ball to second guess direction of the market place.