According to a recent analysis

...the average healthcare provider networks of health plans offered on the health insurance exchanges under the Affordable Care Act include 34% fewer providers than the average commercial health plans offered outside the exchange.

Source: "Exchange Plans Include 34 Percent Fewer Providers than the Average for Commercial Plans," Avalere Health Press Release, July 15, 2015, http://avalere.com/expertise/managed-care/insights/exchange-plans-include-34-percent-fewer-providers-than-the-average-for-comm