There is a startling difference between the prices that university libraries must pay for academic journals owned by commercial publishers and the prices for journals owned by professional societies and university presses. The Eigenfactor subscription cost tool tracks subscription costs of scholarly journals and relates these to measures of journal influence.

Recall that the Eigenfactor score measures the total influence of a scholarly journal. All else equal, as a journal doubles in size its Eigenfactor score doubles. We measure the value provided by a scholary journal as the ratio of Eigenfactor score to subscription cost:

       Cost Effectiveness = k * Price / Eigenfactor.

To make this number easy to interpret, k is an normalizing constant equal to 100 divided by combined price of all journals in the field. Normalized in this way, the average journal in the collection has a cost effectiveness CE=1. Lower values of cost effectiveness represent better deals.

In the search results, the journals are sorted by cost effectiveness (CE). If a subscriber wanted to maximize the value of a collection given a fixed budget, she should purchase journals in this order until the budget is exhausted. The blue bars at right show how much of the total Eigenfactor of the journals in your search you will have obtained when buying the journal in question and all more cost-effective journals. The green bars show how much of the total cost of purchasing all of the journals in your search you will have spent when buying the journal in question and all more cost-effective journals. . As illustrated in the title image above, by subscribing in order of cost-effectiveness, one can often obtain 80% of the total Eigenfactor in a field while spending less than 25% of the cost of subscribing to everything in that field.