Source: U.S. Bureau of Labor Statistics
The Federal Reserve Bank of St. Louis seasonally adjusts this series by using the 'x12' package from R with default parameter settings. The package uses the U.S. Bureau of the Census X-12-ARIMA Seasonal Adjustment Program. More information on the 'x12' package can be found at http://cran.r-project.org/web/packages/x12/x12.pdf. More information on X-12-ARIMA can be found at http://www.census.gov/srd/www/x12a/.
Federal Reserve Bank of St. Louis and U.S. Bureau of Labor Statistics, All Employees: Advertising, Public Relations, and Related Services in Chicago-Naperville-Arlington Heights, IL (MD) [SMU17169746054180001SA], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/SMU17169746054180001SA, September 22, 2018.