From his analysis in his previous article, Dr. Bruce concluded that, to be reliable, evidence must be based on data sets that meet two criteria: First, the number of observations must be large enough that one can be certain that a representative sample has been drawn. And, second, the data set must include individuals drawn from all of the comparison groups that are of interest.

In this article Dr. Bruce uses these two criteria to identify a set of research reports that he considers to be reliable; and he summarises the findings of these reports with respect to the impact that each of spinal cord injuries, chronic pain, visual and hearing disabilities, and brain damage have on both education and earnings.