A zero value for the index indicates that the national economy is expanding at its historical trend rate of growth; negative values indicate below-average growth; and positive values indicate above-average growth.
For further information, please visit the Federal Reserve Bank of Chicago's web site:
Source: Federal Reserve Bank of Chicago
Release: Chicago Fed National Activity Index
Federal Reserve Bank of Chicago, Chicago Fed National Activity Index: Three Month Moving Average [CFNAIMA3], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/CFNAIMA3/, August 29, 2015.