Global Multihazard Total Economic Loss Risks Deciles is a combination of six surfaces. These surfaces include each of the total economic loss risks deciles of the six hazards considered in the study (cyclones, droughts, earthquakes, floods, landslides, and volcanoes) of which only the top three deciles, the most hazardous, were retained (deciles 8-10). In the combined surface, each of the six hazard decile values function together as a unique means of identifying and grouping grid cells. The item Value serves as a numeric identifier of these various unique, decile-based combinations. Theoretically, any results of aggregate analyses are applicable only to the inter-hazards decile combination and not to the individual grid cell. The population per grid cell (item Pop) is based on Gridded Population of the World, Version 3 (GPWv3). The area per grid cell (item Areakm), in square kilometers, is calculated by subtracting from the area of the grid cell those areas identified as being permanently inundated using VMAP (0). The deciles of population density are determined by dividing the population per grid cell by the area per grid cell and classifying the resultant range of values into 10 classes of an approximately equal number of grid cells. VMAP (0) is also utilized to determine the length, in kilometers, of any major roads or railroads.
A multihazard index (item Indexmhz) is generated by summing all the decile values of the individual hazards. The multihazard index itself is not classified into deciles and has a theoretical range of 8-60.
Building upon a methodology presented by Sachs et al. (2003), a Gross Domestic Product (GDP) value (US $2000, purchase power parity adjusted (PPP)) is estimated for each grid cell. The process begins by determining the contribution of each subnational unit to national GDP using data of varied origin. The ratio of the subnational production to the national GDP is the contribution rate.