The underlying data is currently provided by Ward's Automotive Group.Further information on the use of auto unit sales in the preparation of PCE estimates can be found in U.S. Department of Commerce, Bureau of Economic Analysis, Personal Consumption Expenditures, Methodology Paper Series MP-6 (1990). This index is the seasonally adjusted annual sales of domestic made light vehicles sold in the US, in Millions. Domestic made light vehicles including cars and light trucks that are manufactured in the US, Canada, and Mexico. These figures are calculated as follows: the monthly sales divided by the SAAR factors (The Seasonally Adjusted Annualized Selling Rate) provided by the Commerce Department. The SAAR factors adjust for seasonal changes in salse and annualize the figures, making comparisons of the monthly data more meaningful. Please see ATSL for all auto sales statistics. Data prior to 1991 is taken directly from the Commerce Department. Data revisions due to seasonal factor revisions were done by the Commerce department on 9/1/04 for the period 1/2000 - 7/2004. Revisions were done on 2/18/04 back to 1993.