First published by Money Metals here: https://www.moneymetals.com/news/2018/07/03/stock-market-investor-margin-debt-reaches-new-high-001564

The world is standing at the edge of the financial abyss while most investors are entirely in the dark. However, specific indicators suggest the market is one giant RED BLINKING LIGHT. One of these indicators is the amount of margin debt held by investors.