Health insurance plans that limit the number of hospitals and doctors that patients see make up the majority of Obamacare plans, and plans are expected to become even more restricted in 2018, according to an analysis published Thursday by the consulting firm Avalere Health.

The firm found that 73 percent of plans that will become active in 2018 have more restrictive networks, up from 68 percent in 2017 and 54 percent in 2015. Creating narrow networks of providers is one way that health insurance companies keep costs in check, both to their bottom lines and for their customers. For Obamacare customers, it can mean losing coverage for a particular doctor that they had been seeing for years, or in some cases only receiving coverage for medical providers that are further away than other options they would otherwise have in their area.