Differences in the reporting units of data from various sources and changes in units over time are common difficulties that appear in the analysis of geospatial data. For example, in every U.S. Decennial Census many tracts are split, merged or changed in other way from the previous boundaries to track population increase or decrease. The main problem is to find a way to harmonize data to the same geographic unit so that information from different sources and times can be analyzed. This way it would be possible to perform a simple cross-sectional comparison of data in one year with another year.
Therefore, Social Explorer produced reallocated U.S. Decennial Censuses on 2010 Geographies following the present need for cross-sectional comparison of historical decennial data. Reallocated decennial datasets produced by Social Explorer are basically U.S. Decennial Censuses as they are currently available on Social Explorer, but in this case on 2010 Geographies. U.S. Decennial Censuses datasets on 2010 Geographies were obtained by combining U.S. Decennial Censuses with interpolation weights provided by Professor John Logan from Longitudinal Tract Data Base (LTDB). This section provides general information on how U.S. Decennial Census on 2010 Geographies have been produced, more preciselly what decennial census datasets and interpolation weights were used and how LTDB interpolation weights have been estimated.