The numerous sources of wildfire ignitions cause headaches for many utility operator. It can be difficult to justify and defend spend on mitigation programs without determining the risk buydown. This exercise can be made more complicated with novel mitigation techniques are considered for which there is little data on past performance. To address these challenges, SCE evaluated the effectiveness of several wildfire mitigation programs for its transmission system, including underground, covered conductors, and combinations of other activities such as increasing phase spacing, replacing poles and crossarms, adding bird guards, and implementing post-type insulators. Using first principles engineering-based models, the effectiveness, in terms of percentage reduction in expected ignitions, was calculated for key drivers of ignitions, including vegetation contact, animal contact, balloon contact, wire-to-wire contact, and pole and crossarm failure. Integration with reportable ignition data is used to determine overall mitigation effectiveness for mitigation programs. These mitigation effectiveness values are used to determine risk-spend efficiency (RSE) and make decisions on the most effective use of resources to reduce wildfire risk. This presentation will discuss the process of determining mitigation effectiveness using both quantitative risk analysis techniques and subject matter expert input, and how to use mitigation effectiveness values to prioritize risk reduction programs. The benefit of combining engineering models with observational data will be highlighted.