The ASEC acronym is puzzling.

Does anyone know why the CPS Annual Social and Economic Suppliment is always abbreviated as ASEC rather than ASES?

I suspect much of the reason for this is path-dependency. What is now referred to as the ASEC Supplement, was originally called the “March Supplement”. This name refers to the fact that the CPS contains many supplements and the March Supplement was one of these. Eventually, many wanted to recognize that the March Supplement actually included individuals surveyed in other months than just March and the current name, the Annual Social and EConomic Supplement was born. Thus, today many refer to this sample as the ASEC Supplement.

At first I did not see how your answer waas relevent. Then I read it more carefully, and saw that your are suggesting that the proper reference would therefor be to the ASEC Suppliment, and not merely to the ASEC. Though it still seems to me that it should be spelled ASEc (small c) in that case.