An audit report on a city’s Law Department (Austin, Texas) collected several useful performance measures for litigation group. [http://www.ci.austin.tx.us/auditor] I have slightly modified the various listings.
Number of claims received
Number of lawsuits received
Percent of cases (lawsuits and claims, which are mutually exclusive) resolved without payment
Average settlement amount per claim
Percent of claims settled (the converse is percent of claims moving into litigation)
Percent of cases resolved with favorable disposition (Rees Morrison: subjective test sometimes)
Lawsuits per litigation lawyer
Many law departments might consider keeping these metrics. Using several of them allows you to create an index.