In any case, here's two links. One's from Drexel University, the other is a meta-composition of resources by an organization connected to the Kennedy School at Harvard. Educate yourself.
[1] https://drexel.edu/now/archive/2016/December/Black-Men-3-tim...
[2] https://journalistsresource.org/studies/government/criminal-...
The 2.5x number isn't really disputed, it is the reason for it & the policy that is proposed because of it that is contentious.