Calculation of the Center of Population for Bloomington
Center of Population
Jason Phegley standing near the population centroid
The City of Bloomington's Information and Technology Department GIS Division has calculated the center of population for Bloomington, Indiana using a method adapted from that used by the United States Census Bureau. The United States Census Bureau calculates the centers of population for counties in the United States, each of the fifty states, the District of Columbia, and for the nation.
The attached pdf (Method for Calculating Population Center for Bloomington (PDF 30.11 KB)) provides the method used by the City of Bloomington ITS Department's GIS Group to calculate the center of population for Bloomington, Indiana and its results.
The center of population, or population centroid, can be thought of as the point at which an imaginary, flat, rigid, and weightless surface representation of the city would balance if weights of equal size were placed on it so that each weight represents the location of a single person. While this does suggest something about the location of the center of gravity of the city's population, it is not intended to be the only or the dominant measure of the city's population distribution.
The calculation was carried out using the City of Bloomington's Geographic Information System and U.S. Census Bureau population data collected during the 2000 decennial census. Based on this data and method of calculation, the center of population is located at approximately 86° 31' 28.094" West and 39° 9' 33.197" North. In locally descriptive terms, it is just north of Bryan Park near E 1st St.
Geographic Center
In contrast, the geographic center is at 86° 31' 0.298" West and 39° 10' 16.137" North on the IU campus near the intersection of E 10th St and N Jordan Ave. The geographic center can be thought of as the point at which an imaginary, flat, rigid, and uniformly weighted surface representation of the city's corporate boundary would balance. The population center is several blocks south and west of the geographic center.
See both of these points on a map
Uses of this Information
We estimated that approximately 63% of Bloomington's population is clustered within 1.8 miles of this point. This kind of information can assist us in determining how the relocation of various services can impact the majority of our city's population.
Rick Dietz, ITS Director, further explained, "Determining this point can assist the City geospatial analysis applications and decision-making. To use a current example, using this point one can determine that for the average Bloomingtonian the distances to the current Hospital location and to the proposed relocation site are 0.83 miles and 3.36 miles respectively."
Historic Information
Bloomington served as the center of population for the United States in 1910. According to the Census Bureau, the country's center of population was located within Indiana for six decades between 1890 and 1940, the longest of any state. During this time, the center drifted in a generally southwesterly direction until, when in 1950, it was determined that the nation's center of population had moved into Illinois.