MDVIP is the largest and most organized company practice wide scale retainer medicine today. Their business model is fee for non-covered services, which basically means that the retainer fee is for additional care, not covered by CMS, but Medicare is still billed when appropriate.
(State Reported Data Jan 1 Jun 30, 2005)
Now, I appreciate that in general the population of MDVIP might be more affluent than your typical medicare patient. However, it is logical that when doctors spend vastly more time with their patients, clinical improvements are bound to result. (pay for performance anyone?) Perhaps the numbers would change if more doctors practiced this model, but the trend would likely remain the same.
Such a reduction in admissions would go a long way in decreasing the burden of a physician shortage.