The program document should begin with a description of your community and of the library's history. This can be derived from such existing documents as your Planning Process, an annual report or a published history of the Town or Library. Keep in mind that your primary audience is the Architect and his or her colleagues.
Libraries can choose to produce plans for service based on their service population or their official municipal population. However, calculating your "Service Population" can be complicated, depending on your community. There is more than one way to determine what your service population is. Keep in mind that no method is exact; all result in an estimate rather than a hard number. In general, these estimates result in a truer reflection of the library’s actual use patterns than the strict use of census population.
1. Use a percentage based on your circulation
Use your ILS reporting data or other in-house statistics to calculate the percentage of your total circulation that applies to nonresidents. Then add that percentage to your municipal population figure.
For example, if your library is in a municipality with a population of 5,000 and 20% of your circulation goes to cardholders who live outside your municipality, then add 20% to 5,000 (5000 * .20 = 1000) to get a Service Population of 6,000.
This estimate should work for most libraries unless you have high nonresident circulation, such as in resorts or areas with very high cooperative borrowing. These libraries may want to use one of the alternate methods below:
2. Add the population of surrounding unserved or cooperating areas
If, through familiarity and observation, you know that a significant portion of the residents of an adjacent town or towns use your library, you may add the population of the town or towns to the municipal population.
3. Use actual nonresident cardholder statistics
For resorts that draw significant usage from other states or countries, it may be best to use local statistical data to determine the actual number of nonresident cardholders and add the figure to the municipal population.
4. Use your actual census population in the end
If none of these situations applies to you, or if your town is unlikely to support construction of a larger building, then using your official municipal population is perfectly valid. Just be aware that, with transient populations and cooperative borrowing programs, your library may be undersized for the actual number of users.
But remember: if you use one method to determine your service population for a particular question on your grant application, you must use the same method for all calculations. Consistency is crucial.