The concept of the center of population as used by the U.S. Census Bureau is that of a balance point. The center of population is the point at which an imaginary, weightless, rigid, and flat (no elevation effects) surface representation of the 50 states (or 48 conterminous states for calculations made prior to 1960) and the District of Columbia would balance if weights of identical size were placed on it so that each weight represented the location of one person.
Reference Maps
<h6>Mean Center of Population Relative Shift by Decade</h6> This series of plots provides a way to view the variations in movement and distance from one mean center of population to another. In these slides, the compass on the right marks the starting decade for each pair of centers. The second decade's center is plotted in relation to the compass point, with the length and angle of the line indicating the relative distance and directionality of movement. The final slide highlights the decade with the greatest distance of movement (1860), shortest distance (1920), most northerly direction (1870), and most southerly (2010).
<h6>Centers of Population Computation Methodology</h6> Methodology used by the U.S. Census Bureau for the computation of the centers of population from 1950 to 2010.