It would depend on which option you choose 50% 75% or 100% and the age of the spouse in relation to the employee.
The info I have is older, dated 1997, but is probably close to what it is today.
For the 50 percent option
age of spouse /percent payable to employee
20 years younger / 80.0
15 years younger / 82.4
10 years younger / 84.0
5 years younger / 86.00
same age / 88.00
5 years older /90.00
10 years older / 92.00
Your surviving spouse receives 50 percent of your reduced benefit.