Catchments can be defined based upon a number of factors, including distance to the facility, actual travel time to the facility, geographic boundaries or population within the catchment. In a distance based catchment, the area serviced will often depend on the number of visits expected to that institution by each individual. For example, it may be more acceptable to have a larger catchment for a hospital where any one individual will have few annual visits in comparison to a school where visits will be daily and hence desired distance would be closer.