Demographic Data and Mobility Research

The efficient delivery of public transportation requires knowledge of the physical location of individuals who may benefit from service. Furthermore, given the dynamic nature of modern society, the design and operation of public transportation systems, as well as their oversight, must take into account changes in their community to properly accommodate changing needs in the presence of limited resources.

In this study, the cohort-component method of population projection is used to project changes in the size of various groups in five-year increments from 2005 to 2025 for each of North Dakota's 53 counties. Knowledge of the size and distribution of these groups, seniors, students, the disabled, and those without vehicles, within the state should aid policy makers and community transportation managers design a public transportation system that meets the changing mobility needs of the state's residents. In addition to providing projections of the North Dakota's population, the model, once calibrated, can also be used to project populations for other U.S. counties with data available to the general public.

Population projections are made by a large numbers of organizations, most often government agencies. For example, North Dakota population projections by county from 2005 to 2020 were the subject of a 2002 study by Rathge, Clemenson, and Danielson. This study relies on more robust migration data which was made available only recently and accounts for data problems in a unique way. No previous study has projected the size of certain groups of people that are of specific interest to decision makers and researchers in public transportation in North Dakota.

This paper is divided into three parts. The first presents a current demographic profile of North Dakota which is valuable as a starting point for those unfamiliar with the size and distribution of subpopulations that traditionally face mobility challenges. This information is also needed to project future population sizes using the cohort-component method. The second section reviews the cohort-component method of population projection, the most common method used for calculating future populations. The third part of the paper presents the projected size of subpopulations of interest to public transportation researchers. Included as appendices are population projections by age and gender from 2005 to 2025 as well as for special population groups facing greater mobility challenges than the general population.

The geographic level of interest in the study is the county level. The reason for this is four-fold. First, as a rural state, many of North Dakota transportation providers serve large geographic, often multi-county, regions. Second, in many rural areas the efficiencies that may arise by coordinating service at the multi-county level are of importance. Thirdly, some of the data needed to project populations with the methodology used is not available at the local level. Finally, many of North Dakota's communities are so small that if the cohort-component were used at the sub-county level, illogical results would be generated.