1998-04-02 The dataset now contains data
files for Waves 1 and 2 only. The combined data file has been
eliminated. Data definition statements for SAS and SPSS have been
prepared, and documentation is now available as a PDF file.
2005-11-04 On 2005-03-14 new files were added to one
or more datasets. These files included additional setup files as well
as one or more of the following: SAS program, SAS transport, SPSS portable,
and Stata system files. The metadata record was revised 2005-11-04 to
reflect these additions.
1990-10-16 ICPSR data undergo a confidentiality review and are altered when necessary to limit the risk of disclosure. ICPSR also routinely creates ready-to-go data files along with setups in the major statistical software formats as well as standard codebooks to accompany the data. In addition to these procedures, ICPSR performed the following processing steps for this data collection:
- Standardized missing values.
- Checked for undocumented or out-of-range codes.
2006-03-30 File CB9401.ALL.PDF was removed from any previous datasets and flagged as a study-level file, so that it will accompany all downloads.