Introduction

The collective holdings of libraries everywhere seem, at first glance, to be little more than an abstract notion. It's something that we can easily grasp as a concept, but they are nevertheless immeasurable and it's beyond our ability to attach specific properties or characteristics to them. But aggregating and analysing library data – bibliographic descriptions and holdings information – can make the conceptual concrete, and in doing so, provide valuable intelligence to librarians as they organise, steward, share and preserve their collections.

A collective collection is ‘the combined collections of two or more institutions, viewed as a single, distinct resource, usually through aggregation and analysis of metadata about the collections’ (Lavoie et al., 2020, 982). The purpose of collective collection analysis is to understand and, ultimately, more effectively manage collections at scale – that is, collections that span the boundaries of any single institution's local holdings. Collective collections are of ever-increasing importance to libraries as they seek opportunities to find new sources of efficiency by leveraging scale, while at the same time discovering new opportunities to leverage and amplify local collection strengths in a collaborative setting.

Collective collections are integral to shared print programmes, like the Eastern Academic Scholars’ Trust (https://eastlibraries.org) or the Research Collections and Preservation Consortium (https://recap.princeton.edu), where groups of libraries co-ordinate management of their collective print holdings. They also lie at the heart of resource sharing networks like Borrow Direct (https://ask.library.jhu.edu/faq/44698), where materials and users are connected beyond the boundaries of local offerings.