IBNR reserves estimate the cost of claims that have occurred but are unknown to the insurer, along with expected development on reported claims. They are established actuarially rather than on individual files.
IBNR is largest in long-tail lines where reporting lags are measured in years.
Alternative Names:
IBNR, IBNR Reserve
Why it Matters?
IBNR is where long-tail liability creates the greatest uncertainty for carriers, since latent disease and abuse claims can surface decades after the policy period. Underestimating IBNR is the mechanism by which historical liabilities produce present-day reserve strengthening, which is a recurring pattern in asbestos, environmental, and abuse coverage. It also explains carrier caution about writing coverage in categories with long reporting tails.
Frequently Confused with
Related terms
Frequently asked questions
Why is IBNR largest in long-tail lines?
How does IBNR relate to adverse development?
