= Annual loss expectancy (ALE) is the most important criterion when deciding whether to accept residual risk, because it represents the expected monetary loss for an asset due to a risk over a one-year period. ALE is calculated by multiplying the annual rate of occurrence (ARO) of a risk event by the single loss expectancy (SLE) of the asset. ARO is the estimated frequency of a risk event occurring within a one-year period, and SLE is the estimated cost of a single occurrence of a risk event. ALE helps to compare the cost and benefit of different risk responses, such as avoidance, mitigation, transfer, or acceptance. Risk acceptance is appropriate when the ALE is lower than the cost of other risk responses, or when the risk is unavoidable or acceptable within the organization's risk appetite and tolerance. ALE also helps to prioritize the risks that need more attention and resources.
References = CISM Review Manual, 16th Edition, Chapter 2: Information Risk Management, Section: Risk Assessment, page 831; CISM Review Questions, Answers & Explanations Manual, 10th Edition, Question
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