The Chicago Mercantile Exchange (CME) has been operating in the Loop since 1898, just 27 years after the Great Chicago Fire. The exchange was part of the city’s rebirth and helped establish Chicago as a financial hub. Now, we see the opposite of rebirth with Chicago’s population shrinking. And the $66 billion CME may not be around to help with future renewal: The company has rewritten the terms of its lease so it can leave the city if politicians pursue “ill-conceived” public policy. “We’re in a very strong position,” CME CEO Terry Duffy said in a recent interview. “If we...