Looking at the chart below, the data comes from two sources. The first, represented by the dotted line, are the population estimates for Herkimer County over the last 20 years. The Population Estimates program is run by the Census Bureau and provides an annual "estimate" of the population based largely on the number of local births, deaths, and migration that occurred within, in this case, Herkimer County.
The second source of data are the two spikes - one for the 2000 Census and one for the 2010 Census. These come from the census counts (which in reality are technically estimates as well) which were produced as a result of the massive decennial census efforts. A similar effort will be part of the 2020 Census.
If you look at the estimates in the chart below (the dotted lines) it's interesting how, over the 10 year span between decennial censuses these estimates appear to follow a pattern. As the decade progresses, the estimates seem to have had an historical tendency to undercount Herkimer County's population.
The difference between the 1999 Estimate and the 2000 Census is around 1.7%. This suggests that the estimate program was off by as many as a thousand people from what the actual population (as determined by the 2000 Census) was.
And again, after what appeared to be a decade of declining population between 2000 and 2009, lo and behold, the 2010 decennial census shows that the county population had risen slightly from the prior decennial number. The Estimate for 2009 was more than 2,200 people short of what was found in the 2010 Census, and underestimate of nearly 4% .
So now we come to 2018 and the most recent population estimate in the chart. The 2018 estimate suggests Herkimer County has lost as many as 2,700 people since the 2010 Census - BUT IS THIS ACCURATE? Historically, the estimates data has a track record of underestimating the county's population. The reasons for this are not clear, but the pattern is troubling.
Come next year, or early 2021, when the Census Bureau releases its counts for Herkimer County, it wouldn't be surprising to see that the Estimates Program had again underestimated the actual population of the area and an updated version of this chart would show another upward leap from the the 2019 estimate to the 2020 Census count.
