A housing unit in the CPS is interviewed for four consecutive months and then dropped out of the sample for the next eight months and is brought back in the following four months. So, in any given month, one-eighth of the housing units are interviewed for the first month. When the system has been in operation for a full year, four of the eight rotation groups for any month will have been in the survey for the same month, one year ago. Matching information and Stata .do files from NBER Working Paper T0247 by B. Madrian and L. J. Lefgren are available for March-to-March Annual Demographic File matches but can be modified for use in matching CPS Basic Monthly Data. Census Technical Paper such as 66 and 63 contains more information about Design and Methodology.
All data files follow the naming convention cpsbYYYYMM where YY is the year and MM is the month. Here we offer the original files and documentation from 1978 on, and Stata .dta and .csv files for 1989 on.
The file layouts are basically the same for the following periods: 1976-1988, 1989-1993, 1994-1997,1998-2004, and 2017-2020 and 2020+. In March 2021 the following variables had their prefixes changed from 'PE' or 'PR' to 'PT' in order to reflect that they are top-coded: PTIO1OCD, PTIO2OCD, PTERNHLY, PTERNWA, PTERN2, & PTERNH1C, but the layout is the same. Refer to CPS Basic Monthly Footnotes for year specific notes.
The 1976-1988 data documentation calls every group of six Characters a Word. To convert Words and Characters into plain characters multiply the number of previous Words by six and add the number of character positions within the designated Word. That will give the location of the first character of the variable of interest. For example, State is in Word 3, Characters 5-6. 2 previous words * 6 = 12 + 5 = 17 = the starting location of State.
Weekly hours/earnings are not included in these files from 1976-1983. From 1976-1978, these variables are available in the May Extracts. From 1979 on, these variables are available in the Merged Outgoing Rotation Groups.
Usually, the documentation from January applies to an entire year. Exceptions are 1984-1985 and 1994-1995. The January 1984 documentation is used through to June 1985. The July 1985 documentation applies to the remainder of 1985. For 1994-1995, the January 1994 documentation is used through August 1995. The September 1995 documentation serves for the rest of the year.
All variables are numeric (mostly byte) EXCEPT hrsample,hrsersuf and h_id.
Thanks to David Card at Berkeley for providing the 1989-1993
NBER internal Users can access the data from a UNIX shell at /home/data/cps-basic2