Monthly Revisions: Each month, a preliminary estimate for the current month and a revised estimate for the immediately preceding month are released. After the initial revision, no further revisions are made to a month until more complete source data become available in March, June, September, and December.
Quarterly Revisions: The releases in March, June, September, and December contain revised estimates for the previous six months to incorporate more comprehensive and updated source data.
Annual Revisions: Each June, historical data are revised to incorporate newly available and revised source data, changes in definitions and classifications, and changes in estimation methods. Seasonally adjusted data are also revised to reflect recalculated seasonal and trading-day adjustments.
Other Revisions: The release for December statistical month contains revisions to goods for January through November of the most recent year; the release for January statistical month contains revisions to both goods and services for all months of the most recent year. These revisions result from forcing the seasonally adjusted months to equal the annual totals.