They obtained the numbers from NOAA. See below:
"We found the numbers for our visualization from the National Oceanic and Atmospheric Administration (NOAA), which tracks the frequency of natural disasters, their total property damage and the resulting number of deaths. The numbers represent cumulative damage from each category of natural disaster between 1980 to 2017. NOAA has its own sophisticated methodology for how it accounts for these figures. They include both insured and uninsured losses that would not have happened had such an event not taken place. Of course, there’s considerable uncertainty involved in any such counterfactual estimate, but the research is backed by career scientists and economists with a sophisticated understanding of statistics."
[Note: I think tropical cyclones should be named hurricanes. Cyclones are found in the Pacific Ocean.]
