I am an undergraduate in the US applying to REUs in mathematics. Every REU I am applying to through MathPrograms has a section where you can choose to fill out your gender/race, along with a message of the form
The U.S. Department of Education requires [university X] to report on the racial or ethnical composition of its student enrollment. Information on individual students is held in strict confidence. Self-identification is entirely voluntary.
It is not a secret that REUs want to encourage higher participation of minority groups, and indeed the web pages of some programs say things like, "Members of underrepresented groups are especially encouraged to apply."
I am a white male from a suburban area. Clearly this is not going to boost my application, so my question is, could there be much benefit in choosing "decline to answer" on these questions?