In some circumstances, this metric can help describe the likelihood that the impact will be different than expected, the RISK dimension of impact. For more on the alignment of IRIS metrics to the five dimensions of impact, see IRIS+ and the Five Dimensions of Impact (https://iris.thegiin.org/document/iris-and-the-five-dimensions/). No single metric is sufficient to understand an impact; rather, metrics are selected as a set across all dimensions of impact. The selection of metrics to measure and describe the five dimensions should be based on best practice and evidence.