2005 was a record year for hurricane devastation in the United States (San Luis Obispo Tribune, No- vember 30, 2005). Of the 26 tropical storms and hurricanes in the season, four hurricanes hit the mainland: Dennis, Katrina, Rita, and Wilma. The United States insured catastrophic losses since 1989 (approximate values read from a graph that appeared in the San Luis Obispo Tribune, November 30, 2005) are as follows:

  Year         Cost (in billions of dollars)        

Construct a time-series plot that shows the insured catastrophic loss over time. What do you think causes the peaks in the graph?