CLICK ON CHART TO ENLARGE
This chart from Advisors Perspectives/dshort.com looks at the S&P 500 and margin debt (inverted) over the past 20-years. When the spread was wide back in 2000 & 2007 and started narrowing (investors reducing margin exposure), stocks started to sell off.
This chart updates that the spread is now at historical levels. Should this spread start narrowing quickly, it would send a short-term caution message to stock market bulls.