A key technical indicator is sending a signal that it hasn't since 2007, suggesting to one technical analyst that even after a 10 percent decline in the past three months, the S&P 500 still has further to fall.
Jonathan Krinsky of MKM Partners is looking at the S&P's 12-month moving average, which averages out the prior year into just 12 data points.
"Because it only takes data once a month, it tends to take out a lot of the false signals," Krinsky said. "It's a very slow-moving average; it takes a long time to change directions. But when it does, we think you want to take notice."
The moving average has just turned from positive-sloping to negative-sloping for the first time in since 2007, Krinsky said. He views that as an important sign of the market's loss of momentum from high prices.