The Campbell and Cochrane Collaborations were created to reveal the evidentiary status of claims focusing especially on the effectiveness of specific interventions. Such reviews are constrained by the population of studies available and biases that may influence this availability such as preferred framing of problems. This highlights the importance of attending to how problems are framed and the validity of measures used in such reviews, as well as the importance of reviews focusing on questions concerning problem framing and the accuracy of measures. Neglecting such questions, both within reviews of effectiveness and in separate reviews concerning related claims, results in lost opportunities to decrease avoidable ignorance. Domains of avoidable ignorance are suggested using examples of Cochrane/Campbell reviews. Without attention to problem framing, systematic reviews may contribute to maintaining avoidable ignorance.