According to a recent survey of large employers,

44% currently have an on-site clinic in at least one of their locations, and 9% are expecting to build a clinic next year. Source: "Large U.S. Employers Project a 7% Increase in Health Care Benefit Costs in 2014, National Business Group on Health Survey Finds," National Business Group on Health News Release, August 28, 2013, https://www.businessgrouphealth.org/pressroom/pressRelease.cfm?ID=214