In January of each year, the Federal Reserve Bank of Philadelphia revises historical data for the Business Outlook Survey after calculating new seasonal adjustment factors. Because survey responses are characterized by seasonal patterns, new seasonal factors are calculated annually based on the addition of a complete year of data. While this year's revisions altered levels of the indexes for certain months, the pattern of change in most series was not significantly affected. The current general activity index remained positive for the first seven months in 2010, fell below zero for the months of August and September, then recovered to positive readings the remainder of the year. This pattern was not altered by the revisions. The largest revisions occurred for the general activity index at the end of the year. The revisions decreased the levels of the current activity index in November and December 2010 by about 4 points.
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