I put both tables into the default gdb and used the ObjectID. That was after attempting to join the crime data table many times to other tables with no success. So I either selected the wrong census file or Im not setting up my table correctly, I guess?
Tim: The join field you should be using is GEOID. Unfortunately the GEOIDs in the two files are from different states.
OBJECTID is not a valid join field, it is the internally managed ID for every geodatabase table and in most cases should be avoided for joins because it can be modified by the system.
I take that back, the GEOID in these files seems to start after the text US. I think 14 and 15 are different years or something.
So what you need to do to join the tables is to add a new text field in both tables for Census tract, and calculate it to the matching Census GEOID. I think the easiest way is using a Python expression, like this, which starts at the 10th character and drops off the last digit, which is apparently census block group.