PLS staff looked at the holds filled and not filled over a 6 month period from October 2013 to March 2014 inclusive. During this period over 390,000 holds were fulfilled or remained unfilled.
The graph below shows the "fill rate" for these requests. It shows us that while only 17% of requests were filled in the 1st month, 44% of requests were filled within 2 months, 67% were filled within 3 months & 85% were filled within 4 months. These figures will change from time to time, but this 1st set of measures gives us a starting point from which to measure our performance.
From my experience in libraries, being able to fill 67% of all requests within 3 months is a very high success rate. It also gives us some preliminary information when talking to customers about the sorts of waiting times that they can expect - on average at least.