Manipulation of codes by both insurers and providers to shift reimbursements in their favor is one reason why the American healthcare system struggles to control costs, according to a new book excerpted in New York Times Magazine.

The book—written by former Times reporter and the current editor-in-chief of Kasier Health News, Elisabeth Rosenthal, MD—doesn’t put all of the blame for runaway healthcare spending on “indecipherable” medical billing. But it does argue that while hospitals, health systems and insurers find ways to financially benefit through coding, patients, especially those without high-quality insurance, are caught in the middle.

Individual doctors don’t like this system, but Rosenthal wrote their own professional associations are part of the problem.

“The American Medical Association owns the copyright to CPT, the code used by doctors. It publishes coding books and dictionaries. It also creates new codes when doctors want to charge for a new procedure. It levies a licensing fee on billing companies for using CPT codes on bills. Royalties for CPT codes, along with revenues from other products, are the association’s biggest single source of income,” she wrote.

Read the full excerpt here: