Introduction

Traditionally, collection development in libraries has followed a “just in case” model, with librarians carefully selecting and curating collections for their communities. While some suggest that interlibrary loans (ILL) represent an early form of “just in time” collecting (Walker & Arthur, 2018), in recent decades there has been a shift towards “just in time” collection development in the acquisition of e-resources for academic libraries, where materials are acquired as requested rather than “just in case” they are needed. With this method of acquisition, materials are discoverable to the library user despite the fact that the library does not own the material (Cramer, 2013). While the first few moments of use might be provided for free, continued use by the user (or by subsequent users) triggers either a short-term loan or a purchase, subject to the terms of the agreement between the vendor and the library (Cramer, 2013). 

In a context of budget cuts and a reduction of physical collection space, academic libraries have pursued “just in time” acquisition as a method of alleviating concerns about the non-use of materials, which were bought speculatively using “just in case” collection development (Sung & Sung, 2020), while vendors have hoped to monetize the entirety of the process – from viewing, to rental, to purchase – and reduce a perceived loss of income due to the practice of interlibrary loans (Machovec, 2015). “Just in time” acquisition is commonly known as demand-driven acquisition (DDA), yet the term DDA has also been used interchangeably with patron-driven acquisition (PDA). While it is recognized that PDA does not always occur through “just in time” acquisition, this chapter uses the term DDA to refer to both “just in time” and patron-driven acquisition, reflecting the literature’s interchangeable use of these terms and the predominantly PDA-driven nature of DDA.

While this method of collection development has become more common, many concerns around its use remain. With libraries viewing this method as a way to save money and vendors viewing this as a way to increase profits, relationships between vendors and libraries have at times been strained as pricing models and agreement terms have changed. The practice of short-term loans has been particularly challenging as it comes with both significant costs and benefits and has perhaps been the portion of the vendor agreement most heavily modified over the last decade. “Just in time” collection development also raises concerns inherent to patron-driven acquisition, such as the quality and diversity of the resulting collection and the de-professionalization of librarianship, as well as concerns inherent to e-resources more broadly, such as controlled digital lending agreements or librarian control over collections. These concerns will be discussed in more detail in the next section.

This chapter provides an overview of the background and current context of non-serials DDA collection development within academic libraries, some current challenges and proposed responses, and highlights some resources for further reading. This chapter will focus on “just in time” acquisition as it applies to e-resources, but readers should note that “just in time” collection development has also been applied to print collections (England & Anderson, 2019; Walton et al., 2022) and in public libraries (Costello, 2017).

Background and Current Context

Demand-driven acquisition began in the early 2000s as academic libraries experimented with on-demand purchasing of ILL requests (Fischer et al, 2012). DDA then rose to prominence in the late 2000s, when a rise in ebook use and the reduction of physical library collection space coincided with budget cuts and the 2008 recession (Walker & Arthur, 2018; Machovec, 2015). While the advantages (and disadvantages) of ebooks are discussed elsewhere in this book, it should be noted that patrons of university libraries increasingly use – and expect to be available – e-resources, and academic libraries looking to manage physical space limitations can find this format advantageous (Cramer, 2013). Additionally, with the advent of instantaneous (or near-instantaneous) delivery systems, library patrons are increasingly expecting that this will also be their experience at the library (Price & Savova, 2015). It is within this context that DDA plans have been developed and offered, and given the technological advancements of the last few decades, it is likely that this development was a natural progression from vendor approval plans.

At its most basic level, “just in time” e-resource acquisition functions as an expansion of the library’s catalogue to include records and metadata for materials that the library does not own, but which are available for immediate access through purchase or loan (Cramer, 2013; Costello, 2017). This distinction in ownership is indistinguishable to the library user, but is generally visible to library staff through identifying characteristics in the catalogue record’s fields (Sung & Sung, 2020). When a user requests access to the material, it is at that point that a loan or purchase is triggered. For the user, this process is invisible, but administratively the process is much more complicated as vendor and library agreement terms are highly customizable. In addition to retaining control over the pool of DDA-available materials through the use of approval plans or inclusion and exclusion parameters, librarians can also exert control over DDA purchases through negotiating the terms of loan agreements, purchase triggers and purchase ceilings (Costello, 2017).

While there is a need to recognize that circulation statistics do not adequately address in-house material use (Rose-Wiles & Irwin, 2016), research has indicated that around 30-40% of librarian-selected materials in academic libraries never circulate (England & Anderson, 2019; Rose-Wiles & Irwin, 2016). Additionally, research has indicated that a high proportion of circulation is accounted for by a small number of titles (Rose-Wiles & Irwin, 2016), with some suggesting that 80% of materials account for 20% of circulation (Trueswell, 1969). It is thought that by offering DDA, libraries can mitigate concerns about unused materials while simultaneously making available a wide breadth of resources at low cost, for the library will only pay for those materials which are actually used (Cramer, 2013). Additionally, short-term loans provide instantaneous access to library materials – unlike interlibrary loans which can have lengthy delays – while also having the potential to be less costly than participation in ILL programs, particularly as ILL programs try to reduce wait times for books through adjustments to programs such as the use of courier services (Price & Savova, 2015). For vendors, the advantage of offering DDA is the potential to further capitalize upon e-resources: the same resource can be rented (perhaps multiple times) as well as purchased, cannot be sent out to other institutions through ILL due to licensing restrictions, and, as with approval plans, the vendor can hope to shape library purchase behaviour through its DDA offerings and agreement terms.

In recent years, tensions between vendors and libraries over DDA plans have increased. There has been frustration over the ever-changing landscape as both libraries and vendors experience growing pains in the development of these plans and programs. Vendor and publisher profits did not materialize as expected (Machovec, 2015; Seger & Allen, 2015), resulting in significant changes to the structure of short-term loan pricing models and rising costs for institutions, sometimes to unsustainable levels (Buck & Hills, 2017). Additionally, some vendors have reduced their short-term loan offerings (Machovec, 2015), removing some resources altogether and placing a post-publishing embargo on others (effectively rendering them DDA but under a straight-to-purchase agreement). Challenges in collection management such as concerns relating to patron-driven acquisition, e-resources, and the de-professionalization of librarianship are also inherent in DDA as “just in time” collection development encompasses these intersecting issues.

Despite these concerns, it is generally accepted that as Proquest (2018) says, “DDA is here to stay.” The shape of agreements and options continues to evolve, including “access to own” (Proquest, 2018) options where the eventual purchase price can be offset by loan costs. Many academic libraries consider DDA to be one of a number of acquisition methods, balancing out its benefits and concerns with other strategies such as traditional “just in case” collecting, approval plans, and broader patron-driven requests. These next two sections will discuss in greater detail some of the challenges, and potential responses to these challenges, of using DDA as a collection development strategy.

Challenges

As previously described, many of the challenges inherent to other interrelated aspects of collection management are present within DDA. These challenges include collection quality and diversity, library-vendor relationships and agreement terms, and concerns around ongoing collection management. The section that follows discusses these challenges in more detail.

Collection Quality and Diversity

Concerns around the academic library’s collection quality with “just in time” collection development are reflective of broader patron-driven acquisition concerns. Librarians have expressed concern that in their quest for immediate access to materials, users may create collections that are unbalanced across subject areas, may trigger loans or purchases of materials that will later go unused, are not reflective of the subject focus of the institution, or may simply reflect current trends or “hot topics” (Rogers, 2018; Tyler et al., 2014). Others have critiqued DDA for prioritizing speed and convenience over authority, resource evaluation, and collection longevity (Sens & Fonesca, 2013). In particular, academic libraries have a unique focus that requires consideration of the long-term research value of the collection, which may be unknown to current users or librarians. Given the recognized need in academic libraries to teach searching strategies and to provide reference services (Ingibergsson, 2019), there is also the concern that DDA relies on the user’s ability to use the library’s catalogue effectively (Costello, 2017). Significant concerns have also been raised about whether DDA contributes to the de-professionalization of librarianship or whether it is even an inappropriate strategy for academic libraries (Tyler et al., 2014), with some suggesting that if “your goal is to build a great collection, then [DDA] is clearly no way to go about it” (Rick Anderson in Tyler et al., 2014, p. 685).

Interestingly, research into the use of DDA within academic libraries appears to have alleviated many of these concerns (Tyler et al., 2014; Walker & Arthur, 2018). While some have criticized DDA-related research as being overly optimistic (Sens & Fonseca, 2013) and have urged caution, suggesting a need for a closer examination of vendor-researcher relationships and DDA in general, subsequent research (Tyler et al., 2019) has attempted to address this criticism by providing further evidence of the benefits and quality of patron-driven acquisition, with the comment made that “[g]iving the patrons what they want today may very well be supplying the collection with what it needs for tomorrow” (p 551). In comparing the quality of DDA acquisitions to other collection development strategies as measured by citation counts, Tyler et al. (2019) found strong evidence to support the use of DDA in academic libraries across subject disciplines and user groups while also cautioning that other acquisition strategies can be equally or more effective in certain subject areas (such as the sciences) or among certain user groups (such as undergraduate students). Additionally, some have found that subject coverage and quality are similar to more traditional forms of acquisition (Walker & Arthur, 2018) and others have found an increase in the subject and interdisciplinary diversity (Costello, 2017). Resources purchased through DDA are, on average, used more than those selected by librarians through the “just in case” acquisition, and while DDA-purchased materials tend to have a higher cost per title, the average cost per use is lower due to the increase in use (Rogers, 2018; Walker & Arthur, 2018).

The debate over collection quality continues, with research in other areas of information management indicating that while there is a need to integrate user needs and requests into collection management, this must be balanced with the needs and priorities of the institution (Mills, 2015). Known issues of imbalance and underrepresentation in collections (Morales et al., 2014) are exacerbated by DDA collection development and its link to a lack of diversity in the publishing industry. This lack of diversity exists at all levels of the publishing industry as both supported authors and publishing staff are overwhelmingly white (Price, 2022), pointing to the difficulty of creating a diverse and inclusive collection through patron-driven acquisition based on vendor-supplied catalogue records. It is also known that librarians themselves suffer from a lack of diversity (Morales et al., 2014) and that building inclusive collections requires intentionality and careful thought (Price, 2022); therefore, if an institution is truly committed to diversity and inclusion, it must also be committed to collection development through multiple strategies.

DDA Terms and Vendor-Library Relationships

As previously mentioned, many of the specifics of the DDA terms of agreement are negotiable, or may vary between vendors. Vendors may limit DDA offerings by publication date or by popularity; likewise, libraries may limit DDA offerings through their control of the pool of available resources. Similarly, the degree to which short-term loan terms are negotiable may vary – such as the length of the loan, the number of uses before a loan triggers a purchase, and so on. 

While a full review is outside the scope of this chapter, issues relating to the larger context of ebooks and pricing models are also present within DDA (for a discussion of ebook pricing, please see Chapter 5: The Ebook Pricing War: The Fight for Control Between Libraries and Publishers). These concerns include the issue of transparency to library users as the resource is presented as “owned” (or seemingly “free”), as well as concerns around the licensing of e-resources and digital rights management. For example, vendors may remove purchased or leased resources from their catalogue, or the agreement between the vendor and the library may change or be discontinued; in either case, the result is that previously purchased materials are no longer available, possibly to the detriment or frustration of the user (Burns, 2019). Additionally, terms and costing models have shifted and, in some cases, have become unsustainable for libraries (Buck & Hills, 2017). 

Sens & Fonseca (2013, p. 360) have expressed concern about the “Amazonification of a library’s online catalogue, turning the catalogue into a virtual book store” and question whether vendors could use access to the library’s catalogue to further their own interests by manipulating search results and therefore nudging user purchase behaviour. One well-known example that demonstrates the distinction between publisher interests and the library’s desire for collection quality is the inclusion of academic publisher Wiley’s Dummies series of books in library DDA pools (Jabaily & Glazier, 2019); while some librarians may see this series as an accessible resource for users, others could justifiably feel that this series has no place within an academic library context and diminishes collection quality. To mitigate this concern over “Amazonification”, Sens & Fonseca provide a strong argument for the necessity of librarian-mediated DDA through terms negotiation, purchase monitoring, and so on, and advocate for the role of the professional librarian.

In essence, many of these concerns reduce to the long-standing issues of who controls what and whose best interests are being served, in addition to ongoing conversations in the wider context of what “is” a library and whether collection quality or collection use should be considered the benchmark of an excellent library.

Ongoing Collection Management

The challenge of collection management is to “create collections that are used both broadly and deeply” (Costello, 2017, Ch. 1) while recognizing that different formats and acquisition strategies each have their own strengths. The varied user groups who access academic library materials also have different format preferences and needs (Costello, 2017, Ch. 8), with Costello noting that “[t]here is ample evidence that position in the university, discipline of study, access to mobile devices, comfort with technology, and the purpose for reading may all affect the desire to access ebooks and their usefulness in research.” Additionally, ebook availability and pricing is inconsistent across subject areas; for example, fine arts publications are less commonly available as ebooks (England & Anderson, 2019), while STEM (science, technology, engineering and mathematics) ebooks may be more expensive than books from other subject areas (Costello, 2017). Therefore, collection management is an already complex and challenging endeavour, and DDA systems have the potential to provide significant benefits as well as add another layer of complexity. Both Cramer (2013) and Jurczyk et al. (2019) raise the issue of catalogue record weeding, with Cramer (2013) suggesting that while some vendors may ease the removal of records for materials no longer offered through DDA, monitoring and modifying the catalogue for other reasons – such as new editions – could be more difficult. Jurczyk et al. (2019) also comment that it may not always be possible to remove records to account for duplication with the library’s print collection or e-resources licensed through other means, or for materials that may be out of scope for the institution. Pitcher et al. (2021) have commented on the complexity of DDA agreements and the need to mitigate duplication as well as the concern that titles may be removed from DDA offerings with or without consultation. Additionally, Pitcher et al. (2021) have remarked that catalogue records received from vendors for DDA-available materials may be of lower quality, which increases concerns around how the user’s ability to use and search the library catalogue shapes a DDA collection.

Concerns with ongoing collection management are also reflected through ongoing budgetary concerns. While some of these budgetary concerns can be mitigated through the terms of the agreement with the vendor such as collection or per title price caps, accounting for differences in resource costs across different subject areas, or library usage patterns across different disciplines (Jurczyk et al., 2019), could be difficult. It should also be noted that these budget concerns, along with the other concerns raised in this section, suggest that while DDA currently reduces the cost per use of the material it does not reduce staffing needs or the need for professional librarian involvement in collection management, and instead has the potential to increase the importance of appropriate staffing levels to manage complex DDA agreements and the implications of using this strategy in practice. While negotiating appropriate terms of agreement and a consideration of staffing levels can mitigate some of the challenges raised throughout this section, the next section will discuss further potential mitigations in more depth.

Responses

Understanding that there are many challenges in the use of DDA, it should also be recognized that there is the potential to address these concerns through strategies such as a balanced approach to collection development, newer developments in the field such as the use of machine learning, and the role of advocacy in addressing some of the more systemic issues relating to DDA.

Balance in Collection Development Strategies

Many of the challenges described previously regarding the use of “just in time” collection management point to the need to balance the use of different collection development strategies, crafting a blend of “just in time” and “just in case” methodology (Blume, 2019). While DDA has shown, for now, that it can be useful in addressing budgetary concerns and physical space limitations, it does not alleviate concerns over staffing resources, nor does DDA address the need for diversity within collections. Day & Novak (2019) have suggested that this move toward DDA programs and macro-level purchasing programs highlights the need to reexamine the focus of subject librarians or to consider additional forms of collection development such as an “inside-out” model, where internal institutional resources – digitized resources, Open Educational Resources, and so on – are identified and made available to those outside the institution.

The suggestion has also been made that collection development requires careful monitoring of DDA programs as well as the use of intentional “just in case” acquisitions in order to increase diversity and inclusivity in collections (Blume, 2019). Using DDA as a sole collection development strategy, even with carefully crafted parameters, removes institutional control of the collection and places it firmly in the hands of library patrons and select vendors who may have different goals from the library, despite the assertions of vendors that these goals are one and the same (Proquest, 2018); balancing this strategy with librarian-centred acquisition would work towards maintaining the library’s control over the balance and breadth of library materials.

In any case, it is clear that the task of collection development is increasingly complex and can only be addressed through a balance of strategic initiatives, supported by professional librarians, who must navigate the complex array of (sometimes competing) goals and priorities of library users, library institutions, vendors, and publishers.

Data and Machine Learning

As discussed previously, a significant concern within any DDA-driven acquisition method has been that of collection quality, and a concern within DDA is the complexity of managing vendor agreements as well as the different needs and preferences of users across the academic spectrum. While these are both significant challenges, the use of a DDA collection management strategy also offers an opportunity through its generation of vast quantities of data, which librarians could use to mitigate these concerns.

Libraries have a long history of collecting information about their collections and its users to inform collection analysis (Litsey & Mauldin, 2018). Metrics such as circulation statistics, visitor statistics, collection catalogue data and so on can be used to support analysis of collection quality, user preferences, and more. In the context of ebooks, DDA is rich in real-time data and provides an opportunity for complex analysis of the collection and its use, and allows for the use of a wide variety of metrics (Walker & Jiang, 2019). In recognition of this abundance of data and its potential for improving collections, DDA agreements should be negotiated to ensure that libraries have access to the data generated through this collection management strategy, while simultaneously working to mitigate concerns around data privacy, surveillance, and questions around how this data is used by vendors.

There is also a recognition that analyzing large amounts of data may only be useful at a macro-level, and widespread data analysis may be unsustainable in the long-term as the amount of data continues to increase (Litsey & Mauldin, 2018). Within this context, there is an opportunity for the development of effective machine learning techniques to both monitor collection quality and support collection development (Litsey & Mauldin, 2018; Walker & Jiang, 2019). For example, not only could data analytics be used to report on the impact of DDA purchases on collection balance, but machine learning could indicate a need for librarian intervention by predicting micro-level changes in user behaviour in real-time. As the use of machine learning in libraries is relatively new, this technological advancement requires significantly more research before widespread deployment in libraries, and philosophical and ethical questions remain such as bias in the data or algorithm or issues of data privacy (Lo Piano, 2020). For example, in the library context, the use of a faulty algorithm in collection development could magnify issues of imbalance or diversity within collections.

Advocacy

So far, neither of these responses has adequately addressed the need for inclusive and diverse collections, nor do they support recent moves by many academic institutions to implement Diversity, Equity, and Inclusion (DEI) statements. An increase in the use of macro-level purchasing and limited collection budgets could be creating an already challenging environment in which to diversity collections, and the concerns previously described with patron-driven acquisition show that reliance on a DDA strategy could be exacerbating this issue. Additionally, these responses do not address the significant challenges with DDA and e-resources such as short-term loans, pricing agreements, or licensing.

As the concerns raised here with DDA intersect with other areas of collection management as well as reflect broader concerns about a lack of diversity within librarianship (Morales et al., 2014; Price, 2022), so too must the response be more broadly defined; perhaps advocacy, with the goal of wider systemic change, would be appropriate. This need for advocacy and broader change has been reflected in the 2022-2025 strategic plan for the Canadian Association of Research Libraries (CARL) which states that CARL intends to be a leader in advocacy for concerns such as digital access, and suggests that principles of “inclusion, diversity, equity, and accessibility” will be a guiding principle of their work (CARL-ABRC., n.d.). While both CARL and the Canadian Federation of Library Associations (CFLA) have advocated in regard to issues of copyright and e-resource pricing, work toward addressing the imbalance and lack of diversity within the publishing industry have been less apparent but are no less necessary (Price, 2022). Additionally, this advocacy does not address the need to diversify those within the librarianship profession (Morales et al., 2014), though this conversation has been ongoing within the profession itself. In summary, while this advocacy is a good start, it is not enough; without diverse voices in all aspects of these interlocking parts of collection development, it will be much harder to develop inclusive and diverse collections. 

Conclusion

“Just in time” collection development has progressed from an experimental strategy to one which is highly prevalent in academic libraries, particularly with e-resources. While library users have benefited from the ready access to materials and libraries have benefited from a decreased cost per use of materials, as agreement and pricing terms change over time these benefits may diminish. Many of the challenges inherent in e-resources and patron-driven collection acquisition spill over into DDA, such as concerns over collection longevity, diversity, inclusion, and the de-professionalization of librarianship. While these are significant challenges, they can be mitigated through the appropriate blending of collection development strategies and a recognition of the shifting role of librarians, and highlight the role and potential of advocacy in addressing these concerns and working towards systemic change. DDA may be “here to stay” (Proquest, 2018), but is only one of many useful methods of collection development.

Sources for Further Reading

For further reading about demand-driven acquisition, please explore the following resources:

Blume, R. (2019). Balance in demand driven acquisitions: The importance of mindfulness and moderation when utilizing just in time collection development. Collection Management, 44(2-4), 105-116, https://doi.org/10.1080/01462679.2019.1593908

After providing a helpful introduction to the background and development of “just in time” collection management, Blume uses a case study at the University of Utah to show how balance in collection development strategies is necessary.

Costello, L. (2017). Evaluating demand-driven acquisitions. Chandos Publishing.

This book includes background information about the development of demand-driven acquisition as well as a discussion of current research about this method of collection development. Additionally, this book highlights special considerations for specific types of libraries.

Price, A. (2022). Barriers to an inclusive academic library collection. Collections and Curation, 41(3), 97-100. https://doi.org/10.1108/CC-05-2021-0018

Price highlights some of the challenges facing libraries attempting to develop diverse and inclusive collections. While acknowledging barriers, Price also suggests ways of mitigating or addressing these challenges.

Proquest. (2018). Why DDA is here to stay: An analysis of the demand-driven acquisition model for libraries [PDF].  https://pq-static-content.proquest.com/collateral/media2/documents/Whitepaper+-+Why+DDA+is+here+to+stay.pdf

Proquest’s white-paper provides a vendor’s perspective on demand-driven acquisition and demonstrates how vendors market these services to libraries.

Tyler, D. C., Hitt, B. D., Nterful, F. A. & Mettling, M. R. (2019). The scholarly impact of books acquired via approval plan selection, librarian orders, and patron-driven acquisitions as measured by citation counts. College & Research Libraries, 80(4), 525-560. https://doi.org/10.5860/crl.80.4.525

Tyler et al.’s empirical study provides a nuanced view of DDA in comparison to other acquisition methods. This paper also provides an in-depth literature review of the context and debates surrounding the use of DDA.

Walton, R., Maudlin, J. & Bunderson, J. (2022). Patron drivers, patron impacts: Investigating potential patron impacts of moving to a patron driven acquisition model for print books. Collection Management, https://doi.org/10.1080/01462679.2022.2030841

Walton, Maudlin & Bunderson provide a thorough background of “just in time” collection development in e-resource acquisition, and describe the shift to the use of this strategy in print acquisition. This paper includes a review of prior research in this area, as well as an analysis of the authors’ experience of print DDA at Brigham Young University.

References

Blume, R. (2019). Balance in demand driven acquisitions: The importance of mindfulness and moderation when utilizing just in time collection development. Collection Management, 44(2-4), 105-116, https://doi.org/10.1080/01462679.2019.1593908

Buck, T. H. & Hills, S. K. (2017). Diminishing short-term loan returns: A four-year view of the impact of demand-driven acquisitions on collection development at a small academic library. Library Resources & Technical Services, 61(1), 51-56. https://doi.org/10.5860/lrts.61n1.51

Burns, D. (July 8, 2019). “Wait a minute Honey, I’m going to add it up:” Kanopies, DRM, and the permanence of the collection. ACRLog. https://acrlog.org/2019/07/08/wait-a-minute-honey-im-gonna-add-it-up-kanopies-drm-and-the-permanence-of-the-collection/

CARL-ABRC. (n.d.). CARL’s strategic focus 2022-2025. https://www.carl-abrc.ca/wp-content/uploads/2022/07/CARL-Strategic-Focus-2022-2025.pdf

Costello, L. (2017). Evaluating demand-driven acquisitions. Chandos Publishing.

Cramer, C. J. (2013). All about demand-driven acquisition. The Serials Librarian, 65(1), 87-97. https://doi.org/10.1080/0361526X.2013.800631

Day, A. & Novak, J. (2019). The subject specialist is dead. Long live the subject specialist! Collection Management, 44(2-4), 117-130, https://doi.org/10.1080/01462679.2019.1573708

England, M. M. & Anderson, R. (2019). Demand-driven acquisition of print books: Applying 21st-century procurement strategies to a 5th-century format. Collection Management, 44(2-4), 95-104. https://doi.org/10.1080/01462679.2018.1564715

Fischer, K. S., Wright, M., Clatanoff, K., Barton, H., & Shreeves, E. (2012). Give ‘em what they want: A one-year study of unmediated patron-driven acquisition of e-books. College & Research Libraries, 73(5), 469-492. https://doi.org/10.5860/crl-297

Goedeken, E. & Lawson, K. (2015). The past, present, and future of demand-driven acquisitions in academic libraries. College & Research Libraries, 76(2), 205-221. https://doi.org/10.5860/crl.76.2.205

Ingibergsson, E. (July 23, 2019). Not finding it in the library? We will try to fill the void! University of Alberta Library News. https://news.library.ualberta.ca/blog/2019/07/23/not-finding-it-in-the-library-we-will-try-to-fill-the-void/

Jabaily, M. & Glazier, R. (2019). Notes on operations experts or dummies? Quality of e-book pool and user selections in a consortial demand driven acquisition program. Library Resources & Technical Services, 63(4), 220-231. https://doi.org/10.5860/lrts.63n4.220

Jurczyk, E., Pagotto, S., Moisil, I., Grewal, K., Cassady, S. & Cato, J. (2019). Long-term usage of a consortial PDA collection: If they choose it, will we use it? Collection Management, 45(4), 287-303, https://doi.org/10.1080/01462679.2019.1702912

Kochan, C. & Duncan, J. (2016). Analysis of print purchase on demand titles ordered via interlibrary loan: A collection development perspective. Collection Management, 41(2), 51-65. https://doi.org/10.1080/01462679.2016.1174653

Litsey, R. & Mauldin, W. (2018). Knowing what the patron wants: Using predictive analytics to transform library decision making. The Journal of Academic Librarianship, 44(1), 140-144. https://doi.org/10.1016/j.acalib.2017.09.004

Lo Piano, S. (2020). Ethical principles in machine learning and artificial intelligence: cases from the field and possible ways forward. Humanit Soc Sci Commun, 7(9). https://doi.org/10.1057/s41599-020-0501-9 

Machovec, G. (2015). The changing landscape of scholarly e-book purchasing. Charleston Advisor, 17(1), 3. https://doi.org/10.5260/chara.17.1.3a

Mills, A. (2015). User impact on selection, digitization, and the development of digital special collections. New Review of Academic Librarianship, 21, 160-169. https://doi.org/10.1080/13614533.2015.1042117

Morales, M., Knowles, E. C., & Bourg, C. (2014). Diversity, social justice, and the future of libraries. Libraries and the Academy, 14(3), 439-451. 

Pitcher, A., Stift, S., Garstad, R., Polkinghorne, S. & Betmanis, M. (2021, June 4). Demand-driven acquisitions: it’s not new, it’s flexible, and it works! https://doi.org/10.7939/r3-fraw-pm87

Price, A. (2022). Barriers to an inclusive academic library collection. Collections and Curation, 41(3), 97-100. https://doi.org/10.1108/CC-05-2021-0018

Price, J. & Savova, M. (2015). DDA in context: Defining a comprehensive ebook acquisition strategy in an access-driven world. Against the Grain, 27(5), 20-24, https://doi.org/10.7771/2380-176X.7177

Proquest. (2018). Why DDA is here to stay: An analysis of the demand-driven acquisition model for libraries. https://pq-static-content.proquest.com/collateral/media2/documents/Whitepaper+-+Why+DDA+is+here+to+stay.pdf

Rogers, K. (2018). Immediacy vs. foresight: A study of patron selected and librarian purchased ebooks at the University of Mississippi Libraries. Journal of Electronic Resources Librarianship, 30(3), 138-146, https://doi.org/10.1080/1941126X.2018.1493995

Rose-Wiles, L. M. & Irwin, J. P. (2016). An old horse revived? In-house use of print books at Seton Hall University. The Journal of Academic Librarianship, 42, 207-214. http://dx.doi.org/10.1016/j.acalib.2016.02.012

Sens, J.-M. & Fonseca, A. J. (2013). A skeptic’s view of patron-driven acquisitions: Is it time to ask the tough questions? Technical Services Quarterly, 30, 359-371. http://doi.org/10.1080/07317131.2013.818499

Serger, R. & Allen, L. (2015). STL: A Publisher’s perspective. Against the Grain, 27(5), 28-30. https://doi.org/10.7771/2380-176X.7179

Shen, L., Cassidy, E. D., Elmore, E., Griffin, G., Manolovitz, T., Martinez, M. & Turney, L. M. (2011). Head first into the patron-driven acquisition pool: A comparison of librarian selections versus patron purchases. Journal of Electronic Resources Librarianship, 23(3), 203-218. https://doi.org/10.1080/1941126X.2011.601224

Sung, N. & Sung, J. S. (2020). Expanding demand driven acquisition: Complete just-in-time approval plan. Collection Management, 45(3), 195-207. https://doi.org/10.1080/01462679.2019.1679312

Swords, D. A. (Ed.). (2011). Patron-driven acquisitions: History and best practices. Walter de Gruyter GmbH.

Trueswell, R. (1969). Some behavioural patterns of library users: the 80/20 rule. Wilson Library Bulletin, 43, 458-461.

Tyler, D. C., Melvin, J. C., Epp, M., & Kreps, A. M. (2014). Don’t fear the reader: Librarian versus interlibrary loan patron-driven acquisition of print books at an academic library by relative collecting level and by Library of Congress classes and subclasses. College & Research Libraries, 75(5), 684-704. https://doi.org/10.5860/crl.75.5.684

Tyler, D. C., Hitt, B. D., Nterful, F. A.,  Mettling, M. R. (2019). The scholarly impact of books acquired via approval plan selection, librarian orders, and patron-driven acquisitions as measured by citation counts. College & Research Libraries, 80(4), 525-560. https://doi.org/10.5860/crl.80.4.525

Walker, K. W. & Arthur, M. A. (2018). Judging the need for and value of DDA in an academic research library setting. The Journal of Academic Librarianship, 44, 650-662. https://doi.org/10.1016/j.acalib.2018.07.011

Walker, K. & Jiang, Z. (2019). Application of adaptive boosting (AdaBoost) in demand-driven acquisition (DDA) prediction: A machine-learning approach. The Journal of Academic Librarianship, 45, 203-212. https://doi.org/10.1016/j.acalib.2019.02.013

Walton, R., Maudlin, J. & Bunderson, J. (2022). Patron drivers, patron impacts: Investigating potential patron impacts of moving to a patron driven acquisition model for print books. Collection Management, https://doi.org/10.1080/01462679.2022.2030841