From the story here from Sally Pipes:
The analysis was conducted by McKinsey for the Department of Health and Human Services. The consulting firm looked at rate hikes in four states: Georgia, Pennsylvania, Ohio, and Tennessee. Premiums in each had doubled or tripled since 2013 -- the year before Obamacare went into effect.
In Georgia, the average premium for the equivalent of a mid-level "Silver" plan for a 40-year-old male went from $94 a month in 2013 to $323 a month in 2017. In Tennessee, it went from $104 a month to $431.