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How do we calculate ILL requests and ILL cost?


The Scenario Overview page shows the number of ILL requests and an estimate of your total ILL cost.  We calculate these using the following steps:


  1. We use your COUNTER file to determine the number of views your institution makes to each journal in a year
  2. For each journal we forecast this number of views for each of the next five years, scaling it by the growth in articles published by that journal over the last five years
  3. We use information we have on your perpetual access, the open access of the journal, and the number of papers available in academic social networks (like ResearchGate) to determine how many of these views will be fulfilled instantly, for free, each year
  4. If the journal is marked as "subscribed" in your scenario, we assume all its remaining views will be via subscription.  Otherwise, we consider that all the remaining views will be fulfilled by "delayed" paths.  These include asking a colleague or author for the paper, looking for a substituted paper, or making an ILL request.  We estimate the percentage of the delayed views based on reports in the literature as 5% -- 1 out of 20 times one of your authors tries to read a paper and isn't able to instantly find the full text, they make an ILL request.  This config parameter ("ILL frequency, as percent of delayed access") can be changed if you think your ILL request rate may be higher or lower. 
  5. For each journal, we average our estimated forecast number of ILL requests across the next five years to get the estimated annual number of ILL requests forecast for the journal
  6. We sum the estimated number of annual ILL requests across all journals to get the total number of ILL requests we expect you to receive annually
  7. To get the total ILL cost, we multiply the number of ILL requests by your price per ILL fulfillment.  This has been set to $17 based on reports in the literature, but can be changed in config settings ("ILL transaction cost") if your price is different.


You can see the ILL requests and price per journal on the Journals tab, and from there you can click on a journal to get a zoomed in view by year.