In our previous post, we mused about changes in country boundaries that can affect the time series of that region, taking up the example of German reunification. Such changes aren’t limited to international borders; they can also occur within a country. FRED has data for subnational units only in the United States. And although state boundaries haven’t changed much, some county boundaries have. The most dramatic changes happen when metropolitan statistical areas (MSAs) are redrawn. In 2010, the U.S. Census Bureau removed Scott County from the Louisville MSA, dropping about 24,000 residents, which can be seen clearly in the graph above.

The Census Bureau doesn’t recalculate population time series, but the Bureau of Labor Statistics adopts new definitions (after a delay) and recalculates its statistics. This is visible in the graph below, which shows the same series, total non-farm employees, with two data vintages. The ALFRED site allows us to see how data are revised over time and in this case shows the data as of March 17, 2014, and March 25, 2016. The difference is the deletion of Scott County.

How these graphs were created: For the first graph, simply search for “Louisville population.” For the second, Go to ALFRED, search for “Louisville employment,” change the graph type to “line,” expand the sample period to 10 years, and change the earlier vintage to 2014-03-17.

Suggested by Christian Zimmermann