There are some theories. A subscriber to my private email list sent me a link to "Crash Course," a compelling study of three fundamental developments, any one of which could drive our world into a devastating tailspin. Two of the three could send the world into a deep, deep depression. If all three were to come into fruition, DJIA 1000 would be a gift.
To grossly oversimplify the three contingencies:
Peak DebtThe full seminar of Crash Course is over 3 hours long. This is the version I recommend. Here is the link: Crash Course
There is a 45-minute version, here is it's link: 45-minute Crash Course
Because I am providing a recommendation and these links doesn't necessarily mean I accept or endorse all of the arguments presented. But remember, the question at issue is what could possibly underlie Prechter's forecast? The thesis in Crash Course is one explanation.