Also it should be worth noting that the sum of the ALT A and ARM totals is actually less then the sum of the Subprimes.
That may be true in terms of total loan value, but you have to remember that the Option-ARMs have had time to age. All during that time, most were piling on more to the principle while the underlying asset securing the loan has dropped in value. The sub-prime happened fairly early on with respect to the drop in house prices. With Option-ARMs and Alt-A’s, the resets are occurring with the underlying asset already down 10-30% depending upon market, and with the Option-ARM, the balance of the loan may have gone up 5 to 10%
The other thing I have noticed is that when comparing a January 2007 graph with the October 2007 graph, it almost looks like some loans were refi’d into Alt-A and Option-ARMs in the intervening period of time. (look at peak values between the two graphs)