These files are from the National Records and Archives Administration. They have estate tax returns merged with income tax returns for the decedents several years prior. While the files have been stripped of identifying information, confidentiality considerations mean that it is unlikely that any more recent files will ever be made available.
Wojciech Kopczuk (of Columbia University) has graciuously provided SAS programs to read the files and translate to SAS binary files. At NBER we have used Stat/Transfer to create Stata versions. The 1974-1977 files were used in the preparation of his paper "Bequest and tax planning: evidence from estate tax returns which is forthcoming in the QJE (as this is written)."
The original 1959 file is in an integer binary format that may make it difficult for users to deal with the NARA supplied files, but the SAS and Stata files should be no problem.
Anyone wishing to use these files should contact me.
feenberg at nber dotte org
19 November 2006