I put up a link to various studies a while back. Feel free to peruse.
My favorite one is about how cops speak less respectfully to blacks than to whites. Published in the Proceedings of the National Academy of Sciences, June 2017.
Here is a link describing how the study was done.
https://phys.org/news/2017-06-police-officers-respectfully-black-residents.html
I will read the study but the time period where the data was analyzed is off the bat interesting.