I. Introduction:

This file provides data showing the seasonally adjusted aggregate Industrial Production index (total manufacturing, mining, and utilities) as it was originally published and subsequently revised during the normal six-month estimation period. Seven time series are included in the file, showing the level of the index as it was initially published as well as its level when published one, two, three, four, five, and six months after its initial release. The estimate published six months after the initial release is usually the same as that published three months after the initial release, except when an annual or major revision was issued. Each time series, by itself, has discrete breaks at the time of annual revisions. Some come when IP has been estimated using a new base year.

II. Data format and file information:

The data file name is revh_sa.txt.

Data format:

Data begin in January 1972 for all of the index levels except the fifth and sixth revisions, which begin in 2007. The ending date for the initial estimate is the year and month of the most recent Industrial Production Index (designated in the data file naming convention, YYMM). Data are written in ASCII format with four decimal places, twelve months of data per line for complete years.

Column
1	double quote
2-12	series code
13	double quote
14	blank
15-18	year in YYYY format
19-25	blanks
26-144	12 months of data (for a complete year), 8 positions including decimal and 4 decimal places, separated by two blanks. The first value on a line is January and the data for the current year continue as far as has been published. If the initial estimate of IP has been published for May, the first revision of IP is available for April; the second revision is available for March; the third revision is available for February; the fourth revision is available for January; the fifth revision is available for December; and the sixth revision is available for November.

The series codes are comprised of two fields, a prefix and an industry code, separated by a period. For this revision history, the only industry included is total manufacturing, mining, and utilities, denoted by the industry code B50001. Only estimates for the seasonally adjusted data are included.

The prefixes used in the variable names (i.e., init., rev1., rev2., rev3., rev4., rev5., and rev6.) denote the timing of the publication of the data.

	init.	Initial index level, published about 15 days after 
		the end of the month.

	rev1.   first revision, published about 45 days after 
		the end of the month.

	rev2.	second revision, published about 75 days after 
		the end of the month.

	rev3.   third revision, published about 105 days after 
		the end of the month.

	rev4.	fourth revision, published about 135 days after 
		the end of the month.  (Usually identical to third 
                revision, except when there was an annual or major
                revision.)

	rev5.	fifth revision, published about 165 days after 
		the end of the month. 


	rev6.	sixth revision, published about 195 days after 
		the end of the month. 

For example, the initial February 2008 value was published in the middle of March 2008. At the same time, the first revision of the January 2008 value was being published.

III. Calculation of growth rates:

Computing growth rates similar to those actually published requires some care. For example, one should divide the initial estimate of February 2008 (published in mid-March 2008) by the first revision of January 2008 IP (also published in mid-March 2008) to get the initial estimate of growth in February 2008. Use the following formulas to calculate the published growth rates for a series:

 Initial growth rate:			100 * ((init[t] / rev1[t-1]) - 1)
						    	      
 First revision of growth rate:		100 * ((rev1[t] / rev2[t-1]) - 1)
						    	      
 Second revision of growth rate:	100 * ((rev2[t] / rev3[t-1]) - 1)
						    	      
 Third revision of growth rate:		100 * ((rev3[t] / rev4[t-1]) - 1)

 Fourth revision of growth rate:	100 * ((rev3[t] / rev5[t-1]) - 1)

 Fifth revision of growth rate:		100 * ((rev3[t] / rev6[t-1]) - 1)

Estimates of the index levels prior to 1992 are only available to 1 decimal place so percent changes calculated from them may sometimes round differently than the growth rates actually published, which are based on unrounded data. The four decimal accuracy provided in the file after 1992 will usually yield a growth rate that rounds to the one published.