Edmunds is a very reliable source.
That's rich coming from you. Aren't you the guy that claims that it is inappropriate to dismiss what someone says based on their past record of being completely off the reservation? Shouldn't the same apply to people you are inclined to agree with? I mean, simply because Edmunds was reliable in the past doesn't mean this particular assessment is reliable does it?
The way I see it, Edmunds and Kelley Blue Book are putting out divergent assessments of the Cash for Clunkers program in an effort to each gain media attention. Now, that doesn't mean that one is right and the other wrong, but where you have a report that makes certain assumptions about what would have happened in the absence of the Cash for Clunkers program, it seems quite important to understand where the baseline figures come from. Without seeing how they determined the baseline figures, I'd be skeptical of putting much stock in the report.