Seasonal Adjustment

Over the year, the size of the Nation's labor force, the levels of employment and unemployment, and other measures of labor market activity undergo sharp fluctuations due to seasonal events including changes in weather, harvests, major holidays, and the opening and closing of schools. Because these seasonal events follow a more or less regular pattern each year, their influence on statistical trends can be eliminated by adjusting the statistics from month to month. These adjustments make it easier to observe the cyclical, long term trend and other nonseasonal movements in the series. In evaluating changes in a seasonally adjusted series, it is important to note that seasonal adjustment is an approximation and initial adjustment must be based on experience.

Beginning in 1992, BLS introduced publication of seasonally adjusted labor force data for the 50 States, the District of Columbia, and Puerto Rico. Beginning in 1996, seasonal adjustment was extended to estimates for the Los Angeles-Long Beach metropolitan area and New York City. In 1998, seasonally adjusted data for census regions and divisions were published.

With the introduction of the LAUS Redesign in 2005, seasonal adjustment occurs within the model estimation process through the removal of the seasonal component. The new modeling approach is used in developing labor force estimates for Census divisions, States, the Los Angeles-Long Beach-Glendale metropolitan division, and New York City. It was extended to six new substate areas in 2005:

• Chicago-Naperville-Joliet, IL metropolitan division
• Cleveland-Elyria-Mentor, OH metropolitan area
• Detroit-Warren-Livonia, MI metropolitan area
• Miami-Miami Beach-Kendall, FL metropolitan division
• New Orleans-Metairie-Kenner, LA metropolitan area
• Seattle-Belvue-Everett, WA metropolitan division

 

Last Modified Date: August 9, 2005