A coevolution model of defensive medicine, litigation and medical malpractice insurance

We model the interactions between physicians and patients, subject to clinical and legal risks, by means of an evolutionary game. Physicians have to choose between two alternative treatments: D (defensive medicine) and ND (non-defensive medicine). D is less risky, but provides a lower expected benefit to the patient. In case of harm, the patient may sue or not sue the physician. Physicians prevent neglicence charges by buying necical malpractice insurance. The dynamics is modeled by a three dimensional discrete time system. We show the game's final outcome could be an equilibrium point where defensive medicine and litigious behaviour vanish, an interior Nash equilibrium or even an oscillatory behavior. Furthermore, we state a "no-chaos" conjecture, supported by analytical, numerical and empirical arguments.