The Insurance Institute for Highway Safety (IIHS), a private nonprofit organization funded by automobile insurance companies and insurance associations, conducts its own testing program and issues its own ratings. NHTSA and IIHS conduct different tests, and neither organization tests all cars on the market. But they do test the volume sellers. IIHS also made it a point in 2011 to test such innovative cars as the all-electric Nissan Leaf and the plug-in hybrid Chevrolet Volt. NHTSA, in turn, tested the 2013 Tesla Model S, which led to a dust-up over the Tesla's claims about the vehicle's safety superiority.
Here are NHTSA's Five-Star safety ratings. Note that you can't compare 1990-2010 vehicles with those from 2011 forward. Starting with 2011 models, NHTSA introduced tougher tests and new ratings in its Five-Star system. The agency says they provide more information about vehicle safety and crash-avoidance technologies.