There has been a lot of banter of late about whether or not the retail investor has been much involved with recent rallies in the stock market.  The bulls argue that the retail investor has not yet joined in and thus when they do they will provide even more buying pressure to push this wave.  Perhaps they will buy in more as this mania goes along.  But critical thought must ask:  if retail investors aren't yet in, then why are margin loans with brokerage houses at peak levels once again.  See More investors take risk of buying stocks with loans-USA today.

The attached chart from contraryinvestor.com says it best.    It is the hallmark of every major market bubble that borrowing to invest becomes widely practiced.