Is the ACO Explosion Really Over?

I’ve always enjoyed using “exploded” to describe how accountable care organizations have grown since the end of 2010. According to David Muhlestein with Leavitt Partners, just a few dozen ACOs existed heading into 2011, and now there are nearly 500 Medicare and private-payer ACOs. I’d classify that as an explosion.
Now, though, it seems as if the explosion has diminished to a dull glow. After CMS named 106 new Medicare Shared Savings ACOs in January, just 35 ACOs have formed through September — which has been called a slowdown in growth.
Mr. Muhlestein offered three possible reasons for this slowdown in a Health Affairs blog, noting that most of the “trailblazing” organizations have already entered into ACO contracts, and the rest of the hospitals, health systems and physician groups are hanging back, waiting for a proven ACO model before taking the risk-bearing leap (I summarized his take here). He called this the “most important” reason for slowed ACO growth. The third, smaller reason he provided was payer delays, including how Medicare now accepts just one class into its Shared Savings Program per year, as well as commercial payers being reluctant to form ACOs.
While it may be true that most of the innovative “trailblazing” organizations have already formed ACOs, before I accept that other organizations are being timid, I’d like to see how many applications CMS received for its 2014 class of Shared Savings ACOs. CMS has not released how many applied, or how many ACOs will be accepted to the program, but some have speculated that the number of applicants could be above 400.