It seems that the variable you are referring to in January 1989 is not the same as the variable used for DURENEMP. One difference involves the universe for the variables, since item 22C doesn’t seem to be restricted to only those who are not working. This could be addressed with some internal programming on our end. Additionally, it also seems that different people are asked different questions as a part of item 22C based on the response to A$WHYLK. The documentation does not seem to be all that clear as to how these different questions are assigned, so it would take a bit of work on our end to figure this out.
Therefore, although these variables clearly measure similar concepts, they are also quite different. That is why DURENEMP is currently only available back to 1994 in the basic monthly surveys. The IPUMS CPS team will look into the possibility of extending this variable back to pre-1994 basic monthly samples. At this point, however, I am not able to forecast when this work will be completed.