Athenahealth, Inc. (ATHN) provides cloud-based business services for health care providers. The company's flagship offering, athenaCollector, automates and manages billing-related functions for medical practices. We believe athena's offering is unique. All clients operate on a single web-based version of athena's software, which allows each client to benefit immediately from regular updates and the collective experience of other clients. This, in turn, helps improve collections and reduce collection cycles. The company's core addressable market is roughly $36 billion, which represents its potential billings as a percentage of U.S. health care expenditures on physician and clinical services. Management announced plans to enter the hospital market with a new service offering that helps manage transitions of care throughout a health care system. We believe this new offering will expand the size of the company's addressable market and enable it to realize management's vision of becoming the nation's health care information backbone. (Neal Kaufman)
From Baron Funds' first quarter 2014 letter to shareholders.