Risk Analysis from a Top-Down Perspective

Most risk analyses begin by considering the behavior of the lowest and most detailed level of all possible events that can be identified in the system under study. Next, risk estimates are made for each event-consequence relationship and aggregated upward to obtain a total risk estimate of the process under study. The aggregation process propagates the errors contained in the detailed risk analyses, and often results in risk estimates whose error ranges are too wide to provide useful information. An alternative approach starts at the highest level of the problem, and identifies the crucial decisions, decision makers, alternatives and parameters. Agreements regarding specific decisions and subsequent actions are sought at the beginning, and what if situations and conflicts are identified in case agreement cannot be reached. The what if situations provide the framework for more detailed and focused studies in critical areas. A variety of analyses, such as a localized version of the bottom up risk analysis approach and sensitivity analysis, focus on these open ended cases to resolve them. Unresolvable decision conflicts include value judgments which risk analysis cannot solve however, by making these conflicts visible, the focus on differences such as these can often force resolution at a higher management level.