| January, 2006 | Craig Hanson |
| May, 2007 | Gilbert E. Metcalf |
| June, 2005 | Steve Ellis, Vice President, Taxpayers for Common Sense |
| May, 2007 | Eric Toder (on commission by WRI and Brookings) |
| November, 1992 | Robert Repetto, Roger C. Dower, Robin Jenkins, and Jacqueline Geoghegan |
| October, 2004 | Friends of the Earth, Taxpayers for Common Sense, U.S. Public Interest Research Group, et al. |
| April, 2006 | Craig Hanson, David Sandalow (The Brookings Institution) |
| September, 2003 | Gilbert E. Metcalf, Tufts University and NBER |
| June, 2005 | Gilbert E. Metcalf, Department of Economics, Tufts University |
| June, 2005 | Craig Hanson |