G. Berz 1991 <p>Great natural disasters, that is, those exceeding the economic capacity of the affected region and requiring national or international assistance, have increased dramatically in number and scope over the past few decades. As the accompanying graph shows, on average, from the 1960's to the 1980's there has been a five-fold increase in frequency of natural disasters, an increase in total economic losses by a factor of 3.3 and a rise of total insured losses by a factor of 5.8</p> application/pdf en U.S Geological Survey Natural disasters and insurance and reinsurance article