According to a recent report from the Commonwealth Fund:

•  Insurers only selling health plans that comply with the ACA's coverage requirements OFF the exchanges spent 77.3% of revenues on medical claims and 14.2% on overhead.
•  Insurers only selling health plans ON the exchanges spent 79.2% on medical claims and 11.7% on overhead.
•  The profit ratio for insurers selling all products ON the exchanges was 2.0%, compared to 2.8% for insurers selling all products OFF the exchanges.
• Taxes and fees were higher for insurers selling all products ON the exchanges, 6.4% compared to 5.0% for insurers selling all products OFF the exchanges.

Source: "Promoting Value for Consumers: Comparing Individual Health Insurance Markets Inside and Outside the ACA's Exchanges," The Commonwealth Fund, June 2, 2016, http://www.commonwealthfund.org/Publications/Issue-Briefs/2016/June/Insurance-Exchanges-Promote-Value