US_mean_center2010      *Mean* center of population of the US according
                        to the 2010 census
US_median_center2010    *Median* center of population of the US
                        according to the 2010 census
block_group2000         Centers of population of US census tracts
                        according to the 2000 census
block_group2010         Centers of population of US census block groups
                        according to the 2010 census
county2000              Centers of population of US counties according
                        to the 2000 census
county2010              Centers of population of US counties according
                        to the 2010 census
state2000               Centers of population of US states according to
                        the 2000 census
state2010               Centers of population of US states according to
                        the 2010 census
tract2000               Centers of population of US census tracts
                        according to the 2000 census
tract2010               Centers of population of US census tracts
                        according to the 2010 census
