What's the difference between not seasonally adjusted and seasonally adjusted numbers?

Seasonally adjusted numbers have been revised to exclude yearly seasonal components. Not seasonally adjusted numbers include these seasonal components. The Kansas Department of Labor publishes the not seasonally adjusted labor force and nonfarm employment data. We also publish the seasonally adjusted and not seasonally adjusted unemployment rate.

Seasonal adjustment is a statistical technique which eliminates the influences of weather, holidays, the opening and closing of schools and other recurring seasonal events from an economic time series. This permits easier observation and analysis of cyclical, trend and other non-seasonal movements in the data. By eliminating seasonal fluctuations, the series becomes smoother and it is easier to compare data from month to month.

When comparing not seasonally adjusted data year-to-year, most of the recurring seasonal events are accounted for in the comparison. For example, when comparing July 2009 and July 2010, both months reflect the closing of school years. Therefore, the difference in employment over the year is due to reasons other than recurring events. The difference in the employment level would be due to events which are specific to that year, such as weather, strikes or some other factors. Because of the mild winter during the early part of 2006, there were reports of increased construction activities causing the construction industry employment to increase earlier in the year than it has historically.

When comparing data month-to-month, it is important to consider seasonal variations which may account for large parts of monthly fluctuations. Month-to-month not seasonally adjusted changes are an indicator of actual changes in labor force and employment and allow users to understand the size of seasonal variations. Using year-to-year changes would perhaps be more useful in understanding changes in the data that reflect events which are non-recurring. Looking at year-to-year changes allows users to decipher changes that occurred due to an increase or decrease in economic activities or other events that do not reoccur on a regular basis.