Below is the description of the variable, which is also available from http://sedac.ciesin.columbia.edu/es/esi/c_variableprofiles.pdf.  The methodology explains the scale – but essentially, the score is an index, but for interpretation purposes, a score of  2 would mean that the equivalent of twice the total population of the country is exposed to two or more potentially high impact hazards.  A score of  0.65 means that roughly two-thirds of the population of Uganda is exposed to 1 or more of the hazards listed.

Variable #: 45 Code: DISEXP Reference Year: 2005
Description: Environmental Hazard Exposure Index
Units: An index of population-weighted exposure to high levels of environmentally-related natural hazards.
Source: The World Bank.
Logic:  Vulnerability to natural disasters is a function of the exposure to hazards (how often and how severe they are), the sensitivity to such hazards (how big the linkages are to social systems), and the resilience within a society to hazard impacts. This measure provides a useful proxy of the exposure term.

Methodology: To calculate the environmental hazard exposure index, data from Dilley et al. were used. Data on exposure to landslides, droughts, cyclones and floods were put into a consistent GIS database. The world’s land area was classified into degrees of exposure to these four hazards. Those grid cells falling into the highest three deciles of exposure were flagged. The number of high-exposure hazards was summed for each grid cell. The values range from 0-4. The resulting gridded data set was then overlaid with a gridded population data set for the year 2000. Each person was assigned a score equal to the number of high-exposure hazards identified in that grid cell. We calculated the sum of personal exposure scores, and divided by the total population, by country. The theoretically possible range was 0-4. The actual index ranged from 0 to 2.04.