Seasonal factors for auto and truck production have been reestimated using final production data through September. Factors have been revised back through January 1997 and extended through June 2000. These factors are used in the current IP revision. The factors will be updated again and extended through December of 2001 when third quarter schedules are released in the spring. Monthly figures for motor vehicle assemblies in millions of units at annual rate are published at the bottom of Table 2A of the G.17 release. The formula for seasonally adjusted annual rates (SAAR) of auto and truck production (in millions of units) for each month is
SAAR = ((NSA data in units/1,000,000) * 12)/(SF * .01).
The not seasonally adjusted (NSA) data are obtained from Ward's Communications, and the seasonal factors (SF), which contain adjustments for holiday and length-of-month effects as well as normal seasonal variation, are shown in the table below.
Seasonal Factors
Trucks
--------------------
Autos Total Light
--------- --------- ---------
1997 JAN 99.26 99.72 99.88
1997 FEB 100.08 102.29 102.54
1997 MAR 97.66 100.20 100.48
1997 APR 115.97 117.60 117.42
1997 MAY 110.43 110.89 111.20
1997 JUN 101.96 101.49 101.42
1997 JUL 72.41 70.00 68.90
1997 AUG 98.74 94.09 93.87
1997 SEP 100.84 103.97 104.17
1997 OCT 119.52 118.76 118.79
1997 NOV 93.81 92.28 92.50
1997 DEC 90.14 89.26 89.22
1998 JAN 89.92 90.24 90.38
1998 FEB 99.97 102.75 103.01
1998 MAR 113.30 116.24 116.59
1998 APR 105.22 106.80 106.62
1998 MAY 104.65 105.43 105.70
1998 JUN 101.49 101.16 101.06
1998 JUL 73.61 66.94 65.41
1998 AUG 99.05 93.84 93.64
1998 SEP 103.40 109.19 109.75
1998 OCT 114.32 113.41 113.42
1998 NOV 94.13 92.48 92.70
1998 DEC 89.92 89.45 89.42
1999 JAN 89.85 90.26 90.41
1999 FEB 99.70 103.02 103.29
1999 MAR 118.50 121.74 122.12
1999 APR 105.10 106.72 106.53
1999 MAY 104.43 105.56 105.82
1999 JUN 111.22 107.67 107.31
1999 JUL 62.83 60.30 59.06
1999 AUG 104.96 102.44 102.51
1999 SEP 104.12 105.50 105.86
1999 OCT 109.02 108.14 108.15
1999 NOV 99.71 97.84 98.05
1999 DEC 89.68 89.61 89.61
2000 JAN 94.71 95.17 95.35
2000 FEB 104.32 108.28 108.56
2000 MAR 118.37 121.85 122.22
2000 APR 94.53 95.91 95.74
2000 MAY 109.68 111.18 111.46
2000 JUN 110.87 110.40 110.20
2000 JUL 60.81 58.98 57.90
2000 AUG 109.58 106.54 106.59
2000 SEP 99.11 96.55 96.68
2000 OCT 114.19 113.47 113.49
2000 NOV 100.04 98.18 98.39
2000 DEC 84.28 84.28 84.29
2001 JAN 99.64 99.96 100.16
2001 FEB 98.94 103.08 103.34
2001 MAR 112.87 116.30 116.64
2001 APR 99.89 101.23 101.04
2001 MAY 115.04 116.99 117.30
2001 JUN 105.65 105.05 104.84
The table below shows a set of seasonal factors on a weekday average basis; the adjustment for the number of production days in a month, or weekdays, is shown separately. (In the past, we only provided seasonal factors on this basis.) Using this information, the formula for seasonally adjusted annual rates (SAAR) of auto and truck production (in millions of units) for each month is
SAAR = ((NSA data in units/1,000,000) * 260)/(weekdays * SFW * .01).
Multiplying by 260, the average number of weekdays in a year, converts the weekday average production to an annual production rate. This formula reduces to
SAAR = (NSA data in units * .026) / (weekdays * SFW).
Seasonal Factors, Weekday Basis (SFW) and Weekdays
Trucks
---------------------
Autos Total Light Weekdays
-------- --------- ---------- ----------
1997 JAN 93.55 93.92 94.01 23
1997 FEB 108.59 111.39 111.70 20
1997 MAR 101.34 103.41 103.82 21
1997 APR 114.21 115.55 115.43 22
1997 MAY 108.48 108.86 109.17 22
1997 JUN 105.23 103.95 103.91 21
1997 JUL 68.27 65.99 64.96 23
1997 AUG 101.82 97.15 96.91 21
1997 SEP 99.42 102.23 102.33 22
1997 OCT 112.26 111.95 112.01 23
1997 NOV 100.68 100.24 100.42 20
1997 DEC 85.33 84.55 84.46 23
1998 JAN 88.59 88.79 88.86 22
1998 FEB 108.58 112.01 112.35 20
1998 MAR 112.42 114.52 115.01 22
1998 APR 103.61 104.90 104.78 22
1998 MAY 107.56 108.29 108.58 21
1998 JUN 100.01 98.82 98.76 22
1998 JUL 69.42 63.14 61.70 23
1998 AUG 102.15 96.94 96.71 21
1998 SEP 101.96 107.35 107.80 22
1998 OCT 112.19 111.74 111.79 22
1998 NOV 96.01 95.71 95.86 21
1998 DEC 85.21 84.82 84.75 23
1999 JAN 92.74 93.00 93.09 21
1999 FEB 108.32 112.41 112.77 20
1999 MAR 112.65 114.77 115.29 23
1999 APR 103.48 104.75 104.63 22
1999 MAY 107.26 108.33 108.60 21
1999 JUN 109.61 103.00 102.55 22
1999 JUL 61.95 60.03 58.85 22
1999 AUG 103.30 101.99 102.09 22
1999 SEP 102.68 104.67 104.96 22
1999 OCT 112.04 111.68 111.74 21
1999 NOV 96.87 96.70 96.83 22
1999 DEC 85.10 85.02 84.96 23
2000 JAN 97.76 97.98 98.08 21
2000 FEB 108.03 112.58 112.94 21
2000 MAR 111.50 114.78 115.14 23
2000 APR 102.40 103.90 103.72 20
2000 MAY 103.32 104.73 105.00 23
2000 JUN 109.19 108.73 108.53 22
2000 JUL 62.74 60.85 59.74 21
2000 AUG 103.23 100.36 100.41 23
2000 SEP 102.26 99.61 99.75 21
2000 OCT 112.46 111.75 111.77 22
2000 NOV 98.53 96.69 96.90 22
2000 DEC 86.96 86.96 86.97 21
2001 JAN 93.86 94.17 94.35 23
2001 FEB 107.18 111.67 111.95 20
2001 MAR 111.16 114.53 114.87 22
2001 APR 103.06 104.44 104.25 21
2001 MAY 108.37 110.21 110.50 23
2001 JUN 109.01 108.39 108.17 21
December 5,2000
Industrial Output Section
Division of Research and Statistics
Board of Governors of the Federal Reserve System
Washington, D.C. 20551