30% fall-off looming for S&P 500: Economist By: CNBC.com News April 03, 2014 at 03:23 AM EDT The U.S.'s S&P 500 is just 9 points off a trigger point that will see it tumble 30 percent, veteran economist Steen Jakobsen told CNBC on Thursday. Read More >> Related Stocks: Sentinelone Inc Cl A Twitter, Inc.