In 2010, the traffic fatality rate in the United States was the lowest since the federal government

Question:

In 2010, the traffic fatality rate in the United States was the lowest since the federal government began keeping records in 1966. There were 43,510 highway deaths in 2005. This number had decreased to 32,788 in 2010. Find the average rate of change in the number of highway deaths from 2005 to 2010.