Fewer than 40% of S&P stocks above 200-day average
One of those longer-term measures monitors the percentage of stocks within the S&P 500 that are holding above their 200-day moving averages. Healthy markets usually don’t see this dip much below 40%, and unhealthy ones don’t see it rise much beyond 60%.
When it falls below 40% for the first time in months, though, that positive momentum usually reasserted itself.
See this report for more detail.