Origin of the 丁级词 list

ElijahW

April 12, 2011, 11:50 AM posted in I Have a Question

A lot of the study tools for the old HSK had vocabulary  listed according to frequency:

甲级词（1033 words）

乙级词（2018 words）

丙级词（2202 words）

丁级词（3569 words）

Does anyone know where these lists came from? Are they the result of legitimate research?

If so, then these lists are still worth focusing on, even though the HSK has 6 new lists to go along with the new levels.