and are more time consuming to process. 3,8 On the other hand, also the
costs of different ILL requests vary significantly, with a huge
difference between straightforward requests and the most
difficult ones. Hence, allocating the same amount of costs to
these different types of requests would be inaccurate.3 Third,
contrary to overall library costs, specific ILL costs have been
extensively studied in the past, frequently as one of the four
general agreed ILL evaluation criteria: fill rate, turnaround time,
user satisfaction and cost. 9 In the following paragraphs, we
summarize the findings of some relevant studies. For a more
extensive overview of ILL cost studies, we refer to Stein.