The purpose of this paper is to examine economic significance as a fourth measure of significance. In addition to describing and operationalising the concept of economic significance, a typology of economic significance indices is presented, including an example of how to compute these measures, as well as how to utilise them in applied research. We demonstrate how interventions that yield no statistical, practical or clinical effects may be economically significant. Economic significance is not only relevant in the majority of educational research studies, but also is more readily understood by policy makers and stakeholders than are the other three measures of significance, thereby facilitating the accountability of educational quality as a shared responsibility.