“We are forbidden from releasing any government files that contain personally identifying information,” said Ray Tyson, a spokesman for the National Highway Traffic Safety Administration. This is the Department of Transportation’s explanation for why it will not release detailed data on the Cash-for-Clunkers program.

The government has been selective about the data it releases. At various intervals, the department has released top-ten lists for cars traded in and purchased under the program. It has also released a complete breakdown of purchase information by brand.