Riskus

Riskus is a theoretical construct in risk analysis used to quantify the cumulative exposure of a system to adverse events over a specified time horizon. It combines the likelihood of events with their potential impacts, producing a single scalar score intended to reflect both frequency and severity across time.

Calculation and interpretation: If events are described by a time-dependent probability density p(t) and an associated impact function i(t), riskus can be represented as the integral from 0 to T of p(t) · i(t) · e^{-δ t} dt, where δ is a discount rate reflecting time preference or uncertainty. A higher riskus indicates greater cumulative exposure. In practice, riskus is often estimated from historical data, expert judgments, or simulation models and used as a supplementary indicator alongside traditional metrics.

Applications: Riskus has been proposed for project planning, environmental risk assessment, supply chain resilience, and finance, where long-term exposure matters beyond point-in-time assessments.

Limitations and considerations: The accuracy of riskus depends on the validity of p(t) and i(t) estimates and chosen horizon T and discount δ. It can undervalue rare but catastrophic events and may be sensitive to modelling choices. It should be interpreted as a relative measure rather than an absolute fatality risk.

See also: Risk, Risk management, Expected value, Value at risk, Expected shortfall, Time-based risk measures.