According to the Insurance Institute, how many of car head restraints fail to stop rear end crashes?

The Insurance Institute for Highway Safety finds that nearly two-thirds of car head restraints tested don’t get the job done when it comes to rear end crashes. The institute tested 75 cars in its research. And the winners include ail Volvos, some top line Audis, Ford 500s, Nissan Sentras, and Subaru Outbacks. The Cadillac DTS, Suzuki Forenza, and seats in the BMW 5 series were among those who received a failing grade.