attorney general and also Harvard Law School professors Archibald Cox and Philip Heymann in an amicus curiae brief. The Supreme Judicial Court of Massachusetts overruled the objections in a unanimous decision. The decision opened the way for widespread adoption of no-fault automobile insurance schemes, a development that was encouraged by the federal Department of Transportation. Overview in United States Most U.S. states have a "traditional tort" liability system for auto insurance in which recovery is governed by principles of provable negligence. However, twelve U.S. states and the Commonwealth territory of Puerto Rico require policyholders to operate under a "no-fault" scheme in which individuals injured in automobile collisions are limited in their ability to seek recovery from other drivers or vehicle owners involved in a collision. An additional 8 states have an "add-on" system in which the insured party retains the right to sue. In 2012, RAND Corporation published a study which found that costs were higher in no-fault systems. In the case of economic (medical and wage-loss) damages, most no-fault systems permit injured parties to seek recovery only for damages that are not covered by available first-party insurance benefits. In the case of non-economic (pain-and-suffering) damages, most no-fault systems permit injured parties to seek compensation only in cases of exceptionally "serious" injury, which can be defined in either of two ways: A quantitative monetary threshold that sets a specific dollar (or other currency) amount that must be spent on medical bills before a tort is allowed. Disadvantages of this threshold are: (1) that it can encourage insured parties (and their medical providers) to exaggerate medical costs through over-utilization, and (2) that, unless indexed, it can become ineffective over time because of inflationary effects on medical costs. A qualitative verbal threshold that states what categories of injuries are considered sufficiently serious to permit a tort (e.g., death, or permanent disability or disfigurement). The advantage of the verbal threshold is that it removes any incentive to inflate damage amounts artificially to meet some preset monetary loss figure. The primary disadvantage is that seriously injured claimants may be barred from compensation where their injury does not match their state's threshold definition language. In terms of damages to vehicles and their contents, those claims are still based on fault. No-fault systems focus solely on issues of compensation for bodily injury, and such policies pay the medical bills for drivers and their companions no matter