Although appealing to more refined tastes, art as a collectible has not always performed so profitably. During 2015, an auction house sold a painting for a price of $1,140,000. Unfortunately for the previous owner, he had purchased it three years earlier at a price of $1,720,000.

What was his annual rate of return on this painting? (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.)