Here are some gain curves for untinted Behr UPW #1050.

The samples were made up by applying three coats of the paint to a piece of white bristleboard using a hard white trim roller.
A pearl clear coat produces even more gain but I don't have any measurements. Here is a comparison photo of UPW with no top coat, a poly top coat, and two coats of pearl pearl clear coat.

The pearl clear coat is application is discussed in this
thread in post #16 if you are interested.