The share of S&P 500 stocks above their 50-day and 200-day moving averages has plunged. About 45% of members closed September above the 200-day line, and roughly 25% above the 50-day, after both measures sat above 70% as recently as July. The 50-day line moves faster, which is why it has fallen furthest.
Source: Bespoke Investment Group (@bespokeinvest)