• Impact is about the influence of libraries and their services on individuals and/or on society.  
  • An easier way of thinking about impact is as the difference or change in an individual or group resulting from the contact with library services (British Standard 3.25) 

Identifying impact 

Bear these two key issues in mind about impact  and library and knowledge services:

  1. The change (impact) can be tangible or intangible and may be difficult to quantify
  2. The impact may be difficult to separate from other influences and prove that the impact was due to the library   

LKSs may only contribute to an impact rather than be solely responsible for it (e.g. length of stay, patient care). 

Proxy measures 

Surrogate or proxy measures of impact may be used to monitor impact.  For example, output data such as attendance, or satisfaction with a service.  

Proxy measure will not demonstrate actual impact

The contributions of LKSs can be monitored via: 

  • Solicited methods such as questionnaires, interviews   
  • Observations that are either structured or informal   

Critical Incident Technique 

The Critical Incident Technique is useful for tying the impact to one particular use of the library and knowledge service.   


Ideally these methods should be used in combination for reliability. 

 The impact of sample size and low response rates 

  • Care needs to be taken when making claims about impact generated from small sample sizes or low response rates.
  • A minimum of 60% response rate has been recommended for samples of physicians to be confident about the claims being made (Urquhart and Turner, 2016) 

Tools to measure impact 

Before measuring impact, check that it is really impact you want to measure. The terminology is complex and often used interchangeably 

A range of tools are available that can be used to measure impact: