Please answer the given financial question based on the context.
Context: the following table provides the weighted average assumptions used in the black-scholes option-pricing model for grants and the resulting weighted average grant date fair value per share of stock options granted for the years ended december 31: .
||2018|2017|2016|
|intrinsic value|$ 9|$ 10|$ 18|
|exercise proceeds|7|11|15|
|income tax benefit realized|2|3|6|
stock units during 2018 , 2017 and 2016 , the company granted rsus to certain employees under the 2007 plan and 2017 omnibus plan , as applicable . rsus generally vest based on continued employment with the company over periods ranging from one to three years. .
Question: by how much did the intrinsic value decrease from 2016 to 2018?
Answer:
-0.5