The ACOs are in effect latter-day health-maintenance organizations—doctors, hospitals and other health-care providers grouped together to provide coordinated care. …

We believe that many of them will not succeed. The ACO concept is based on assumptions about personal and economic behavior—by doctors, patients and others—that aren’t realistic. …

The first untenable assumption is that ACOs can be successful without major changes in doctors’ behavior. Many proponents of ACOs believe that doctors automatically will begin to provide care different from what they have offered in the past. Doctors are expected to adopt new behavior that reduces the cost of care while retaining the ability to do what’s medically appropriate. But the behavior of doctors today has been shaped by decades of complicated interdependencies with other medical practices, hospitals and insurance plans. Such a profound behavior shift would likely require re-education and training, and even then the result would be uncertain. …

The second mistaken assumption is that ACOs can succeed without changing patient behavior. In reality, quality-of-care improvements are possible only with increased patient engagement. Managed care, as formulated in the 1990s by the HMO model, left consumers with a bad taste because the HMOs acted as visible gatekeepers to patient access to care. ACOs, seemingly wary of stirring a similar backlash, allow Medicare patients to obtain care anywhere they choose, but there is no preferential pricing, discounting or other way for ACOs to steer patients to the most effective providers.