Normalised New Zealand natural Disaster insurance losses: 1968-2019

The Insurance Council of New Zealand's Disaster List documents private sector insurance payouts caused by natural perils since April 1968. We normalise these and, where possible, payments made by the Earthquake Commission, a government natural disaster insurance scheme, as if historical events were to impact current societal conditions, defined here as the 12-month period from 1 July 2018. The methodology employs changes in the number, size and nominal cost of new residential dwellings as key normalising factors. Since 1968, earthquakes account for 79% of the normalised losses with the 2010-2011 Canterbury Earthquake Sequence (CES) at NZD20.1 billion the single most expensive event. The redlining of residential suburbs shown to be vulnerable to liquefaction and the introduction of more stringent building codes are estimated to reduce normalised losses for a repeat of the CES by about one-third. More frequent losses due to extreme weather, notably storms of tropical, sub-tropical and extra-tropical origin, when combined and after adjusting for changing societal factors, show no trend over the record length. We explore why an attempt to use the Fraction of Attributable Risk to cost the contribution of anthropogenic climate change to weather-related event losses delivers results inconsistent with most normalisation studies.