route with passengers who did, and others who did not, insist on the driver wearing a belt. They completed the route faster when belted. In addition to risk compensation, Adams has suggested other mechanisms that may lead to inaccurate or unsupportable predictions of positive benefits from seat belt legislation. Case-control studies based on voluntary use of safety aids can attribute to the aid benefits that actually come from the risk-averse nature of those likely to use them voluntarily (confounding), particularly early adopters. Fatality rates are subject to considerable stochastic noise, and comparison of single years or short periods can be misleading. However, after introduction of seat belt laws in many European and American countries, safety agencies did not validate the compensation theory: A 2007 study based on data from the Fatality Analysis Reporting System (FARS) of the National Highway Traffic Safety Administration concluded that between 1985 and 2002 there were "significant reductions in fatality rates for occupants and motorcyclists after the implementation of belt use laws", and that "seatbelt use rate is significantly related to lower fatality rates for the total, pedestrian, and all non-occupant models even when controlling for the presence of other state traffic safety policies and a variety of demographic factors". A comprehensive 2003 US study also did "not find any evidence that higher seat belt usage has a significant effect on driving behavior." Their results showed that "overall, mandatory seat belt laws unambiguously reduce traffic fatalities." Individual liberty Opponents have objected to the laws on libertarian principles. Some do so on the grounds that seat belt laws infringe on their civil liberties. For example, in a 1986 letter to the editor of the New York Times, a writer argued that seat belt legislation was "coercive" and that "a mandatory-seat-belt law violates the right to bodily privacy and self-control". A counterpoint to the libertarian view is that by reducing death and serious injury, mandatory seat belt use and enforcement of seat belt laws results in substantial social benefits. For example, an analysis by the Centers for Disease Control and Prevention found that in 2010 non-fatal injuries to motor vehicle occupants cost the United States $48 billion in medical expenses and lost work. An example is an unbelted driver who kills or injures another road user because he/she slides out of proper seating position and cannot regain control of the vehicle during slippery conditions. Another notable scenario is