Which statement best describes the Annual Rate of Occurrence (ARO)?

• A. The annual probability that a given risk event will occur.
• B. The total expected annual loss.
• C. The number of assets at risk.
• D. The time to recover.

Answer: (A)

The main idea is how often a specific risk event is expected to happen in a year. The Annual Rate of Occurrence (ARO) captures that frequency or likelihood within a 12-month period, and it’s used alongside the potential loss from a single event to estimate annual risk. In practice, you multiply this rate by the Single Loss Expectancy to get the Annualized Loss Expectancy (ALE), which is the total expected annual loss from that risk.

So the option describing the annual probability or frequency of the risk event occurring in one year is the best match. It’s not the total expected annual loss (that would be ALE), not the number of assets at risk (asset exposure), and not the time to recover (MTTR).