The Population Estimates Program annually produces population estimates based upon the last decennial census for general purpose governmental units (ie., Nation, state, county). Each year, we re-calculate the estimates in the time series for previously released years using the most up-to-date demographic components of change and legal boundaries available.
We distinguish the time series by their "Vintage" year, which is the latest year in the time series. For example, if the latest year in the time series of estimates is July 1, 2011, then the Vintage year for all estimates in this time series are identified as belonging to "Vintage 2011." All estimates in Archives are from Vintages that have been superceded by estimates shown in Current Estimates Data.
If you are interested in examining change from year-to-year in the population estimates, you can do so by comparing each year within a particular vintage.