Insurance Loss Analysis of Single Family Dwellings Damaged in Hurricane Andrew
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In recent years hurricanes have caused billions of dollars of damage to houses, putting the insurance industry under severe strain. In order to set appropriate premium rates in future and to guide damage mitigation policies, an understanding of the relationships between insurance losses and types of damage, and wind speed are required. Using loss data from Hurricane Andrew provided by two insurers, relationships have been established between average loss ratios and gradient wind speed for zip code areas. A more detailed analysis of data provided by one insurer enabled average loss ratios and damage severity for building components such as roofs, doors, windows, walls and external facilities to be determined. From this information it was possible to determine a loss magnifier relating the total damage to a building and its contents to damage to its envelope. At gradient wind speeds below 70 m/s and overall loss ratios less than 12% the total damage averaged twice the direct wind damage to the envelope. Above 70 mis the total damage increased to nine times the average envelope damage and resulted in average overall loss ratios greater than 60%. A comparison of the results of this study with the relationship between insurance losses and wind speed developed by Friedman, and used by some sectors of the insurance industry, indicated that such usage would seriously underestimate losses in typical zip code areas of 100 square kilometers. Friedman's relationship might prove satisfactory for a typical county of approximately 2500 square kilometers, the averaging area used by Friedman.