This is a topic on which I haven’t seen much, if any, discussion.
Completion rate is essentially the amount of time USCIS projects it will take them to adjudicate a particular type of immigration petition. For instance, on average, it takes USCIS about 12 minutes to adjudicate an Application for Employment Authorization (EAD) on form I-765. On the other end of the spectrum, it take USCIS about 35 hours to adjudicate a petition for a new EB-5 related regional center.
What we’ve seen, anecdotally, is that the shorter the amount of time it takes to adjudicate a case, the better the odds a mandamus lawsuit will be successful in compelling action and getting a quick decision. This makes intuitive sense as well. If USCIS determines it will take much more time to fight the case rather than decide it, they have a strong incentive to decide it.
Some examples of petition types that have relatively quick completion rates include I-130s, I-485s, I-765s, I-131s and N-400s.
Quick completion rates do not in any way guarantee a mandamus lawsuit will be successful. There are other important factors at play. However, it is a factor that seems to tilt the odds in the favor of the Plaintiff.