From the link:
This is a bit tricky at the moment because of the late reporting. One has to guess what is happening with margin debt behind the monthly market moves. Since the August drop in price is reflected in the margin debt drop (big professional players lightening up, maybe desperately lightening up), and since the market has rallied so far this month, one can guess margin debt may move up a bit here in September but not a enough to head off what is to come.
And since the market likes to fool everyone into complacency at the last possible moment, a new high here would probably be just enough to lock long-term investors in when they should be at least shuffling, if not running, to the exit.
For the history and a chart:
MARGIN DEBT - the same old same old