In practice, the likelihood of occurrence for a particular risk is usually not known with absolute precision because of a lack of information or uncertainty of the situation. As a result, we decided that looking back to the time of contract formation(i. e, the point in time when the facility owner contracted for detailed design and/or construction) on completed projects would be the most useful strategic point to determine the level of risk that existed When taking a retrospective view of risk at a given point in time, uncertainty is no longer an issue because the event has either taken place or not occurred, and the likelihood of occurrence component of risk assessment is no longer an unknown being assessed in a predictive manner. In essence, the retrospective look at risk leads to a determination of relative impact to the project. With adequate input from experts across a multitude of international projects, an aggregate baseline impact factor could be developed for each IPRA element. Then, as a predictive tool, likelihood of occurrence would al ways have to be assessed and the impact component of risk would be either this predetermined aggregate baseline level or a self-determined level by project participants Workshops We decided that the best way to develop reasonable and credible relative impact values for each element was to rely on the expertise of a broad range of construction industry experts. From September 2002 to January 2003, we hosted four risk assessment workshops. Held in various locations in North America, a total of 44 industry executives with extensive international experience reporting results on approximately $23 billion worth of projects from 20 different countries were involved. Participants represented 25 organizations and were made up of 26 contractor and 18 owner representatives. In addition to having an owner/contractor balance, a fairly equitable distribution of project types and locations was achieved Each participant completed a series of documents at the workshops. In addition to personal history, participants were asked to consider and document a typical international project that they had cently completed for the organization they represented. The details regarding the workshops and the projects used for this effort are provided in Cll Research Report 181-11(CII 2003) Workshop participants proceeded in order through the 82 elements with each IPRA element description reviewed in the context of their project. An analysis of the data created a rank-order of the IPRA elements by their relative impact and these were sorted from 1 to 82. Relative Impact designations were developed for the 82 IPRA elements. The overall rankings were broken into five levels of corresponding Relative Impact that were given letter designations ranging from A to E, with A Negligible, B- Minor, C= Moderate, D= Significant, and E= Extreme, corresponding to degrees of impact as defined in Figure 2. The Baseline Relative Impact values of the significant and extreme elements are given in Appendix B of this article. A detailed discussion of this development effort is beyond the scope of this paper; for more information on how these values were developed, please see Cll Research report 181-1l7 In practice, the likelihood of occurrence for a particular risk is usually not known with absolute precision because of a lack of information or uncertainty of the situation. As a result, we decided that looking back to the time of contract formation (i.e., the point in time when the facility owner contracted for detailed design and/or construction) on completed projects would be the most useful strategic point to determine the level of risk that existed. When taking a retrospective view of risk at a given point in time, uncertainty is no longer an issue because the event has either taken place or not occurred, and the likelihood of occurrence component of risk assessment is no longer an unknown being assessed in a predictive manner. In essence, the retrospective look at risk leads to a determination of relative impact to the project. With adequate input from experts across a multitude of international projects, an aggregate baseline impact factor could be developed for each IPRA element. Then, as a predictive tool, likelihood of occurrence would always have to be assessed and the impact component of risk would be either this predetermined aggregate baseline level or a self-determined level by project participants. Workshops We decided that the best way to develop reasonable and credible relative impact values for each element was to rely on the expertise of a broad range of construction industry experts. From September 2002 to January 2003, we hosted four risk assessment workshops. Held in various locations in North America, a total of 44 industry executives with extensive international experience reporting results on approximately $23 billion worth of projects from 20 different countries were involved. Participants represented 25 organizations and were made up of 26 contractor and 18 owner representatives. In addition to having an owner/contractor balance, a fairly equitable distribution of project types and locations was achieved. Each participant completed a series of documents at the workshops. In addition to personal history, participants were asked to consider and document a typical international project that they had recently completed for the organization they represented. The details regarding the workshops and the projects used for this effort are provided in CII Research Report 181-11 (CII 2003). Workshop participants proceeded in order through the 82 elements with each IPRA element description reviewed in the context of their project. An analysis of the data created a rank-order of the IPRA elements by their relative impact and these were sorted from 1 to 82. Relative Impact designations were developed for the 82 IPRA elements. The overall rankings were broken into five levels of corresponding Relative Impact that were given letter designations ranging from A to E, with A = Negligible, B = Minor, C = Moderate, D = Significant, and E = Extreme, corresponding to degrees of impact as defined in Figure 2. The Baseline Relative Impact values of the significant and extreme elements are given in Appendix B of this article. A detailed discussion of this development effort is beyond the scope of this paper; for more information on how these values were developed, please see CII Research Report 181-11