The effectiveness of most crime prevention strategies will remain unknown until the nation invests more in evaluating them. That is the central conclusion of this report. The inadequacy of that investment to date prevents a judgment for or against the effectiveness of the $3 Billion in federal crime funds, at least to a reasonable degree of scientific certainty. Using "rigorous and scientifically recognized standards and methodologies"--the mission Congress set out for this report--the review of over 500 impact evaluations reveals only a han ....