In 2003, Sotheby's the auctioneer sold a mustang 1955 for a price of $10,341,500. The owner who sold the car had purchased the Mustang in 1999 at a price of $12,437,500 from a rich celebrity.

What was owner's annual rate of return on this Mustang from the original purchase to the sale? (A negative answer should be indicated by a minus sign. Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.)