Health insurer Aetna Inc is submitting premium rates to regulators for Obamacare insurance plans for 2015 that generally increase less than 20 percent from 2014, its Chief Executive Officer Mark Bertolini said on Wednesday. "We have rates that are in the zero category. On average, it's in the low double digits, as a rate increase across the population," Bertolini said. Bertolini's comments, made during a Goldman Sachs healthcare conference outside Los Angeles, come as insurers prepare next year's health plans for the insurance exchanges created under the Affordable Care Act, known as Obamacare.