- A large scale study originally undertaken in North America in 1992 by Joanne Marshall
- It became known as the Rochester study and was the first to demonstrate impact of hospital libraries
- The approach was subsequently adapted and used in a range of other studies
- In 2013 the study was updated by Joanne Marshall and conducted on a large scale across North America
- The tool and data sets are publicly available: https://nnlm.gov/mar/about/value
- Similar studies have been undertaken in the UK by Christine Urquhart and Alison Brettle