Bloomberg reports that a large bearish position in U.S. equities that’s been amassed by trend-following funds may prove vital to the next move for stocks, according to a strategist who’s been analyzing markets since the early 1990s.

The S&P 500 Index is now trading within 50 points of its 200-day moving average, a metric that’s proved important when breached in the past for changes in positioning by commodity-trading advisors, known as CTAs, according to an analysis from James McCormick at NatWest Markets Plc.

The firm’s signal, which tries to forecast changes in flows by replicating what a generic trend-following strategy would do, is near its most bearish level and positioning is at its biggest net short since 2016, he wrote in the report.

“This level is certainly worth watching,” McCormick, the firm’s global head of desk strategy in London, wrote.