Six months after new health insurance options took effect for millions nationwide, most Chicago-area hospitals say they haven't seen a noticeable change in the number of emergency room visits. The theory was that people who previously didn't have insurance would no longer go to emergency rooms for treatment; under the Affordable Care Act, commonly called Obamacare, they would make a doctor's appointment, lowering health care costs by reducing ER visits. Emergency rooms charge higher prices for minor illness and injury care than other ambulatory care settings, because they offer more services. But so far, at least, there is little evidence of an impact.