Rainu Kaushal, a professor of medical informatics at Weill Cornell Medical College, led a study published in 2010 in which she and four colleagues followed prescriptions issued by a sample of providers in outpatient settings in New York. The researchers found an astonishing 37 errors for every 100 paper prescriptions, versus around 7 per 100 for those who used e-prescribing software. The Institute of Medicine has estimated annual costs for preventable A.D.E.'s in hospital settings alone at about $2 billion in the United States. Yet only about 36 percent of all prescriptions were delivered electronically in the United States in 2011, according to a report to be published in May by Surescripts, which maintains an e-prescribing network.