Wholesale selling pressure

Perhaps no other figure encapsulates the type of selling pressure witnessed on Monday than the number of stocks falling to their lowest price in over a year. Many times over the years, we've seen that when more than half of a sector trades to a new low at the same time, it's a consistent signal that investors have panicked. 

It doesn't happen very often in individual sectors, and it's even less common when looking at all of them together. That's what we saw on Monday, with over half of securities on the NYSE falling to a 52-week low. It got almost that high on the Nasdaq.

See this report for more detail.