Demand-Driven Acquisition E-books Have Equal Cost Per Use as Print, but DDA Has Much More Active Use Overall


  • Laura Newton Miller Carleton University



demand driven acquisition, dda, patron driven acquisition, pda, ebooks, collections


A Review of:
Downey, K., Zhang, Y., Urbano, C., & Klinger, T. (2014). A comparative study of print book and DDA e-book acquisition and use. Technical Services Quarterly, 31 (2), 139-160.


Objective – To compare usage of demand-driven acquisition (DDA) e-books with print books to help determine if one acquisition model better serves the needs of library users and return on investment.

Design – Case study.

Setting – Library system of a large American public university.

Subjects – 22,018 DDA e-book discovery records, 456 purchased e-book records, and 20,030 print item records were examined.

Method – The researchers examined usage statistics, circulation statistics, and cost measures of DDA e-books and print books. E-books were purchased in 2012 and print books were purchased by the start of the DDA project (January 2012).

Main Results – All but one of the 456 DDA-triggered e-books had repeated use within the first year, totalling 2,484 user sessions. 90% of the triggered e-books had 2-9 user sessions, and over half had at least 4 user sessions. E-books were most used in classes N (fine arts), P (Language and Literature), and R (Medicine). E-books in T (Technology) had a lower percentage of user sessions compared to other subject areas. 712 (3.2%) of the e-books in the discovery pool were used without triggering a purchase. Usage of e-books in the discovery pool (those used but not triggering a purchase) showed a consistent use of e-books by subject. E-books in Class B (Philosophy, Psychology, Religion) were used more in the discovery pool without actually being purchased, suggesting a light use of a wide range of books in this subject area. In contrast, Class R (Medicine) saw less use in the discovery pool than what was actually purchased, suggesting heavier and more focused use of triggered e-books in this area. Only 62.5% of the 20,030 purchased print books included in the study were used in the first 1 to 2.5 years they were added to the collection (i.e., 37.5% were not used in that time period). Half of the print books were used no more than once (once or no use), and more than 90% were used fewer than 10 times. Print books in Class Q (Science) contributed to only 7.5% of the total circulations, suggesting print books are underused in this subject area. 10.2% of total circulation of print books in Class R (Medicine) suggests print books are better used in this area. Print acquisition and use occur more often in classes N (Fine Arts) and P (Language and Literature). The average cost for DDA e-books was of $98.52 per book. The average price per print book was $59.53. The unit cost per print book was $17.73 per use. Depending on various measures, cost per use for e-books ranged from $17.73 to $29.15 per use. (If the measurement included the free use of non-triggered DDA books, the cost per use was $18.07, essentially the same as the print cost).

Conclusion – Both print books and DDA e-books are proportionately distributed across most subject areas. Although DDA and print cost per use are equal, DDA leads to much more active use overall.


Download data is not yet available.

Author Biography

Laura Newton Miller, Carleton University

Assessment Librarian




How to Cite

Newton Miller, L. (2015). Demand-Driven Acquisition E-books Have Equal Cost Per Use as Print, but DDA Has Much More Active Use Overall. Evidence Based Library and Information Practice, 10(1), 89–91.



Evidence Summaries