Over the course of a year, non-seasonally adjusted employment levels go though sharp fluctuations due to seasonal events. The seasonal events are not only weather-driven events such as predictable patterns of freezing weather which reduce construction employment, but also non-weather events such as schools coming back into session and resulting in increased employment of education staff.
Seasonal adjusting is a statistical technique which attempts to eliminate normal seasonal increases or decreases in employment levels. The seasonal adjustments do not factor out all seasonal workers, just the worker level changes expected by reviewing past seasonal employment level changes in the non-seasonally adjusted historical data series. The goal of seasonal adjustments is to make it easier to observe real job growth or declines from one month to another from non-seasonal businesses and from seasonal businesses which hired more or less than they did in the past. The smoothed series works well as long as weather patterns or non-weather related annual event dates do not change to the degree that hiring or job losses appear in different pay periods.
To seasonally adjust data, there must be years of non-seasonally adjusted historical industry data that show clear seasonal patterns. Data for states with high employment levels are much easier to seasonally adjust, since one large business's entry or exit in an industry in that state does not result in as great of percentage change in historical data, which in turn is less likely to change the seasonal patterns.
You may download the data sets of South Dakota seasonally adjusted nonfarm wage and salaried workers for statewide South Dakota and the Metropolitan Statistical Areas (MSAs) from the nonfarm historical database application. Statewide seasonally adjusted data is available back to 1990. Total nonfarm data (without industry detail) for the Sioux Falls and Rapid City MSAs is available back to 1990. Data is provided only when it meets the criteria for publication as established by the Bureau of Labor Statistics (BLS).
For more information on seasonal adjustment of nonfarm wage and salaried worker data, see the U.S. Bureau of Labor Statistics website.
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