In the U.S.A. 21 states and the District of Columbia have statewide mandatory helmet laws for children. 29 U.S. states have no statewide law, and 13 of these states have no such laws in any lower-level jurisdiction either. The territory of Guam made helmets compulsory for all bicycle riders and passengers on 27 February 2012. Israel's helmet law was never enforced or obeyed. A long and sophisticated volunteer campaign led to the revocation of the adult element, in order to allow bike-hiring schemes to work. An official predicted that this would have disastrous health consequences. Mexico City has repealed its helmet law to allow a bike-sharing scheme to work. The mandatory wearing of helmets is frequently supported by medical organizations and by bodies responsible for road safety. Head injury can result in death or disastrous long-term physical and mental disability. Such injuries have happened to cyclists, and such cases have given powerful stimulus to political activity. A helmet testing specialist states that some of these accidents can generate energy levels beyond those used when certifying competition motor racing helmets. One study which examined post-mortem examinations of the twenty cyclist fatalities in Auckland, New Zealand between 1974 and 1984 found that sixteen died of fatal injury to multiple organ systems, including fourteen with fatal brain injuries; four died solely of brain trauma. A 2018 review analysed the results of 21 studies on the effects of bicycle helmet legislation. The meta-analysis results showed that helmet legislation reduced total head injuries by 20%, and serious head injuries by 55%. A motoring breakdown organization has sponsored an initiative by the Bicycle Helmet Initiative Trust which supports legislation, reporting that "in 2009/10 nearly 6,000 young cyclists were admitted to hospitals and of these 40% had suffered head injuries. Around 83% of young cyclists suffering head injuries were not involved in a collision with another vehicle but merely hit their head after falling from the cycle. " In North Carolina, where bicycle helmets are compulsory for children, the North Carolina Department of Transportation publish a fact sheet stating that a bicyclist is killed or injured approximately every six hours and that helmets reduce the risk of head injury by as much as 85% and the risk of brain injury by as much as 88%. The National Highway Traffic Safety Administration reports that in 2006, 773 bicyclists were killed in the US. In a speech arguing for helmet legislation in the UK Parliament, an MP said: "In a three-year period from 2003, 17,786 children aged 14 and under were admitted to NHS hospitals in England because of injuries incurred while cycling"  In the UK, some 8,000 years of average cycling will produce one clinically severe head injury, and 22,000 years one death.