Definition of Terms

Legal Service Area Population

The number of people that reside within the legal service area of the library. The legal service area of a library is the population within the boundaries of the geographic area the library was established to serve.

Attendance at Children’s Programs as Percent of Total Attendance

= (Attendance at Children’s Programs) / (Total Program Attendance)

Libraries provide programs to inform, educate, and entertain their clients, and to promote further library use. This measure relates the number of persons of all ages attending library-sponsored programs directed at children to all persons attending programs of all kinds. It is one indicator of how successful a library has been in planning children’s programs.

Circulation of Children’s Materials as Percent of Total Circulation

= (Children’s Materials Circulation) / (Total Circulation)
This measure compares the circulation of children’s materials to the library’s total circulation. Note that it is a measure of children’s materials circulated, regardless of the age of the borrower. It is helpful to examine this statistic when considering library service to children.

Circulation per Capita

= Circulation / Legal Service Area Population
Circulation per Capita relates the number of library materials lent to the number of persons the library serves. It is annual circulation divided by the library’s legal service area population, and indicates the average number of loans made to each resident annually. Lower Circulation per Capita can be a result of lower Materials Expenditures and Volumes Held per Capita. It is also likely to lead to more ILLs (interlibrary loans) per 1,000 Circulation.

Evening & Weekend Hours as Percent of Hours Open

= (Evening Hours Open + Weekend Hours Open) / (Total Hours Open)
Evening & Weekend Hours as Percent of Hours Open shows the percent of hours the library is open after 5 p.m. and on the weekends, compared to all hours the library is open to the public. (See also Public Service Hours Open per Week, below.)

Public Service Hours Open per Week

Public Service Hours Open per Week is a simple count of hours that the library is staffed and open to the public. For libraries with multiple outlets, this is the total number of hours open per week for all outlets combined. The definition of public library as set forth in Public Library Standards for Colorado and includes the following stipulation: “[A public library must] be open a minimum of 20 hours each week. Some of these hours should be evening and weekend hours to maximize service to the public. Libraries with multiple service outlets should provide at least 20 non-duplicated service hours each week” (p. 2).

Interlibrary Loans per 1,000 Circulation

= (Interlibrary Loans borrowed) / (Circulation / 1000)
Interlibrary Loans per 1,000 Circulation relates the number of materials borrowed from other libraries to the number of materials in the local collection available to borrowers. It is the number of materials borrowed through interlibrary loan divided by total circulation divided by 1,000. A higher figure of ILLs per 1,000 Circulation might indicate better performance by the library as a point of access for information not in the local collection. A lower figure might indicate that the local collection was meeting user needs. The interpretation of this statistic depends on which issue is at hand as well as the actual amount of ILL and circulation activity per capita. Higher levels of ILL and circulation activity favors the former interpretation, while lower levels of such activity favors the latter interpretation.

Local Income per Capita

= (Total Local Income) / (Legal Service Area Population)
Local Income per Capita is perhaps the best single measure of the library’s financial support, as the vast majority of operating income comes from local sources. This is the total local income amount (from city, county, district, or other sources) divided by the number of persons in the library’s legal service area population. Knowing the extent to which libraries are supported by their local funding base is valuable information for public librarians and their governing boards when submitting and defending budgets.

Materials Expenditures per Capita

= (Materials Expenditures) / (Legal Service Area Population)
Materials Expenditures per Capita relates library funds spent on materials for the collection (e.g., books, periodicals, and non-print items, such as audio and video cassettes) to the number of persons the library was established to serve. It is the dollar amount spent on materials divided by the library’s legal service area population, and indicates the average cost per person of purchasing newly acquired materials. This figure does not take into account the cost of processing library materials. Materials Expenditures per Capita is relevant whenever the size or usefulness of the collection is an issue. When addressing this issue, relate other input measures indicating the quantity of materials available, such as Volumes Held per Capita; also relate output measures that indicate the usefulness of materials, such as Circulation per Capita, Turnover Rate, ILL Net Lending Rate, and ILLs per 1,000 Circulation. It is also important to review Materials Expenditures per Capita whenever the population of the library’s legal service area changes quickly.

Materials Expenditures as a Percent of Operating Expenditures

= (Materials Expenditures) / (Total Operating Expenditures)
Materials Expenditures as a Percent of Operating Expenditures Materials Expenditures as a Percent of Operating Expenditures relates the amount spent on the library’s collection to what is spent for overall operations. It is the cost of library materials divided by the amount spent for all operating expenses including materials costs. This measure indicates the proportion of the library’s operating expenditures which is set aside for materials. This may indicate a library’s commitment to its collection. However, an extremely high figure on this measure can also indicate a library’s lack of commitment to paying staff, which is usually a major cost. To interpret this measure, take into account “other operating expenditures.” A library may pay large bills for online utilities and telecommunications services for database searching. For comparisons, use libraries which have similar “other” expenses.

Net Lending Rate

= (Materials Loaned) / (Materials Borrowed)
Relates the number of materials loaned to other libraries to the number of materials borrowed from other libraries through interlibrary loan. It is the number of items loaned divided by the number of items borrowed. It indicates whether the library does more lending (scores of more than 1) or more borrowing (scores of less than 1). “Net Borrowers” may use this figure as evidence of what they gain from participating, while “Net Lenders” may use it to argue for the maintenance of strong collections.

Program Attendance per 1,000 Served

= (Program Attendance) / (Legal Service Area Population)
Program Attendance per 1,000 Served relates attendance of scheduled presentations which are sponsored by the library (on or off library premises) to the population the library is established to serve. It is program attendance divided by the library’s legal service area population in thousands. It indicates the number of residents per 1,000 in the library’s legal service area who attended a library program during the year. This output measure may be relevant whenever the library needs to demonstrate its services to groups.

Reference Questions per Capita

= (Reference Questions per Week x 52) / (Legal Service Area Population)
Reference Questions per Capita relates the annual number of information contacts with a staff member using information sources to the number of persons the library is established to serve. It is the number of reference transactions per typical week multiplied by 52, then divided by the library’s legal service area population. This measure indicates the average number of times a resident of the library’s legal service area received staff assistance in using information sources available at or accessible through the library. Reference Questions per Capita may be relevant whenever the impact of reference service is an issue. Comparing this figure to Circulation per Capita may be useful in evaluating the reference desk as an access point for information available in the local collection. Comparing it to ILLs per 1,000 Circulation and ILL Net Lending Rate may be useful in evaluating access via the reference desk to information that may not be available locally.

Staff per 10,000 Circulation

= (Total Staff FTE) / (Circulation / 10,000)
Staff per 10,000 Circulation relates the size of the library’s staff to the number of items circulated. It is the number of staff in FTEs (full-time equivalents; see Staff per 1,000 Served) divided by total annual circulation in tens of thousands. This statistic measures staff workload relative to circulation.

Staff per 100 Reference Questions

= (Total Staff FTE) / (Reference Questions / 100)
Staff per 100 Reference Questions relates the size of the library’s staff to the number of reference questions the staff handles. It is the number of staff in FTEs (see Staff per 1,000 Served) divided by total annual reference questions (or reference questions per typical week multiplied by 52) in hundreds. This statistic measures staff work load relative to reference services provided.

Staff per 1,000 Served

= (Total Staff FTE) / (Legal Service Area / 1,000)
Staff per 1,000 Served measures the level of staffing relative to the legal service area population. It is the number of library staff in FTEs divided by the number of persons in that area. FTE staff is calculated by adding the total number of hours per week worked by all staff and dividing by 40. In this context, full-time means 40 hours per week, regardless of how many hours per week the library is open. This input measure may be relevant whenever the adequacy of library staffing and staff funding are issues. It is particularly useful when the population or geographical area which the library serves increases dramatically. When that happens, there should be a corresponding increase in staff to offset the population increase.

Staff Expenditures as a Percent of Operating Expenditures

= Staff Expenditures / Total Operating Expenditures
Staff Expenditures as a Percent of Operating Expenditures is the sum of all staff expenditures for salaries, wages, and benefits divided by the sum of all operating expenditures for staff, materials, and other purposes. This measure indicates the proportion of the library’s annual operating expenditures that is spent to compensate staff. Generally, this figure comprises the single largest proportion of operating expenditures. If this figure is extremely high, however, it may indicate a lack of adequate funding for other aspects of library operations; and, if extremely low, it may indicate a lack of commitment to having professionally trained library staff.

Subscriptions per 1,000 Served

= (Serial Subscriptions) / (Legal Service Area Population / 1,000)
Subscriptions per 1,000 Served relates the number of current serial subscriptions carried by the library to the size of the population it serves. It is the number of current serial subscriptions divided by the population served divided by 1,000. This statistic is a measure of the size of the library’s current periodicals collection relative to the population it serves.

Turnover Rate

= Circulation / Physical Materials Held
Turnover Rate relates the number of materials checked out relative to the size of the collection. It is the number of materials circulated divided by the number of physical materials held. Turnover rate indicates how often each item in the collection was lent, thus this measure is relevant to use of the collection. It may be useful to compare this figure to selected inputs such as Volumes per Capita, and outputs such as Circulation per Capita and ILLs per 1,000 Circulation.

Videos per 1,000 Served

= Videos Held / (Legal Service Area Population / 1,000)
Videos per 1,000 Served relates the number of video materials in the library’s collection to the size of the population it serves. It is the number of video cassettes (or disks) divided by the population served in thousands. This statistic is a measure of the size of the library’s video collection relative to the population it serves.

Library Visits per Capita

= (Visits per Week x 52) / Legal Service Area Population
Library Visits per Capita relates the number of annual library visits to the number of persons the library is established to serve. It is attendance at the library during a typical week multiplied by 52 (weeks per year) divided by the library’s legal service area population. This measure may be estimated by counting the number of persons (excluding library staff) who enter or, if preferred, leave the library during a typical week. A typical week is one during which the library is open its regular hours (no holidays) and which is neither extraordinarily busy nor slow. Because Library Visits per Capita indicates the average number of library visits per person served, it is a better measure of public awareness and use of the library than Registration per Capita. Because registration statistics may be out of date and, therefore, questionably valid, attendance statistics reflect actual visits to the library. Taken with Reference, Circulation per Capita, and Program Attendance per 1,000 Served, Library Visits per Capita can be used to develop an annual profile of library use.

Volumes per Capita

= Volumes Held / Legal Service Area Population
Volumes per Capita relates the number of volumes or units in the library’s collection to the number of persons it was established to serve. It is the number of print volumes held by the library divided by its legal service area population. This figure indicates the average number of volumes held for each person in the library’s legal service area population. This input measure may be relevant whenever the size of the library’s collection is an issue. It is particularly useful when the population or geographical area which the library is established to serve changes dramatically. For example, in the latter case, there should be corresponding increases in Materials Expenditures as well as Volumes Held just to maintain the existing ratio of holdings to persons served.