by how much did the intrinsic value decrease from 2016 to 2018?
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. .

intrinsic_value_change = 9 - 18
grant_date_fair_value_per_share = intrinsic_value_change / 18
answer = grant_date_fair_value_per_share * 100