Are disasters more frequent?

Jay Zagorsky, an economist at Ohio State, and NOAA think so. N0AA has recorded 212 disasters since 1980; the damage was over $1.2 trillion. Using NOAA's data Zagorsky calculates the number of billion-dollar disasters since 1980; the results have increased from 2.7 in 1980 to 5.4 in 2016. An additional billion-dollar disaster occurs every four years. But NOAA's data does not account for the growth in the economy in that period. Zagorsky adds that in and concludes  that an additional billion-dollar disaster occurs about every 25 years, not every four years. So the frequency of these natural disasters is increasing, but not nearly as fast as the raw NOAA data suggest.