Part of Mankiw's defense for a gas tax comes from an old CBO report from 2004 which compares the benefits and costs of CAFE to a gas tax. They confirm that a gas tax could cost less than CAFE. ... That conclusion came from the old CAFE model. The model has since been reformed.
I wish Mankiw would stop pushing that out-dated CBO report (from 2004). The entire CAFE model has been revised since then and is in the process (end) of a major overhaul. This overhaual makes that report useless and outdated. I'm waiting for a new CBO report.
Read more here: CLICK ME
Or, for a point by point about what reformed CAFE means for efficiency: CLICK HERE
I'm not saying I think CAFE is THE only way to go, but I am saying that Maniw's use of the old CBO report is misleading. In fact part of the reason for the push of the overhaul was due to this old report. Shame on Mankiw for presenting only partial facts.