CHICAGO—A University of Chicago freakonomics professor told General Electric investors Monday to keep a close eye on recent fluctuations in the heights of competitive powerlifters from Mexico. "Usually we can count on a stable average of 5 feet 8 inches, but last month's quarter-inch drop in height among Mexican dead-lift competitors in the middle-heavyweight division could spell disaster for GE's aviation and software subsidiaries," freakonomist James Duncan said. "But, like anything else, a shrewd investor must always ask himself one thing: How many hot dogs did I eat last year?" Duncan previously gained recognition for tracking first-time home ownership and teenage mothers' gum purchases against the Times Tom Jones Is Played Per Day Index.