There was an error in the 2001 SIPP Wave 4 data-collection instrument that prevented it from collecting the data for the Work Schedule topical module for most of the eligible persons in Rotation 2 of the Wave 4 panel. The instrument correctly collected these data for all the eligible persons in the other three rotation groups.

In the post-data-collection edit, the data were imputed jointly for the entire set of edited variables for the Work Schedule Topical Module for most of the persons in Rotation Group 2 who were eligible for this module. The joint imputation was done by a hot-deck imputation procedure that used persons in the other three rotation groups as donors. The user can identify the members of Rotation 2 who underwent this joint-imputation procedure by using the AALLIMP flag variable (AALLIMP =1 if and only if the person is in Rotation 2 and the data for the entire set of edited variables for the Work Schedule

Topical Module were imputed jointly). Note that the values of the allocation flags for these Rotation 2 persons (for whom AALIMP=1) reflect the values from the donor and not the fact that the data were imputed by the joint-imputation procedure.