Index use per capita measures?
Per capita measures reflect the relative prevalence of library services and library utilization compared with the population being served. These measures have been traditionally used in librarianship to compare libraries serving constituent communities of different sizes. However, per capita measures do introduce certain irregularities which need to be kept in mind when interpreting comparative library statistics and rating systems like the LJ Index. Libraries delivering substantial amounts of services to non-resident users (for instance, libraries serving vacation communities) can show very high per capita service levels. These high levels exaggerate the relative levels of services these libraries deliver. Unfortunately, we do not have statistical tools for reliably identifying and adjusting for these cases in the IMLS data.
