We assessed the effect of provider networks on access to four medical specialties for Affordable Care Act Marketplace enrollees in California. Our approach incorporated a crucial consumer-focused attribute, travel distance, and identified the restrictions on provider access resulting from network design. Our analysis indicated that Marketplace plan networks are narrower than their commercial plan counterparts and feature just over half as many providers. However, there is much diversity in network breadth, depending on consumers' choice of plans and geographic region. Furthermore, network designs often create important access issues for consumers because of what we call "artificial local provider deserts"-geographic areas within networks devoid of providers by design. Consumers in large metropolitan areas are generally guaranteed a significant degree of access and choice, but network design exacerbates limited access for rural areas in which few providers are available to any consumer.
Keywords: Affordable Care Act; California; Coronary artery bypass surgery; Health insurance exchanges; Health policy; High quality care; Hospital quality; Mortality rates; Quality of care; Surgeons.