One criticism of IBC's method, from MIT's John Tirman, a principal research scientist, is that the "surveillance instrument" - the news media - is changing all the time: media organizations add or (more likely) subtract reporters from the field, which was happening in Iraq; reporters were largely confined to Baghdad during the worst violence; and reporters tended to write about spectacular events, like car bombs, when much of the violence was in the form of revenge killings throughout Iraq. "As a result, this technique of totaling up the dead is incapable of accounting for the deaths that were not being recorded, whether by the English-language news media or the chaotic health care system." IBC itself radically changed its method in the middle of the war, switching from two references to one reference in the news media.[28]