Assume that the economy has an $32\%$ chance of booming, a $30\%$ chance of being normal, and being recessionary the remainder of the time. A stock is expected to return $23\mathrm{.}2\%$ in a boom economy, $16\mathrm{.}06\%$ in a normal economy, and $-18\mathrm{.}27\%$ in a recession economy. What is the standard deviation of returns on the stock?

Enter your answer as a percentage, rounded off to two decimal points. Do not enter $\%$ in the answer box.