Codes & Standards - Purchase
Performance indicators can be used for comparison over time within the same library. Comparisons between libraries can also be made, but only with caution. Comparisons between libraries will need to take into account any differences in the constituencies of the libraries and library attributes, with a good understanding of the indicators used, limitations to comparisons, and careful interpretation of the data).
ISO 11620:2014 offers accepted, tested, and publicly accessible (i.e. non-proprietary) methodologies and approaches to measuring a range of library service performance.