It basically comes down to what you're trying to measure. Are you trying to compare people to their peer group, or are you trying to figure out if they've learned the things on the curriculum. They basically switched from the former to the latter. And for good reason, really. How my friends do on the test has no bearing on how much of the material I've learned. Imagine if the driving test worked like that. "You only got 5 minors, but unfortunately for you, most of the other people today got 4 or fewer, so you've failed." Or worse "I know you almost crashed three times and stalled twice, but John ran over a granny, so you've passed."