This is about encoding of the actual codeword range of this family of compressors. So far the number of used bits just gets increased after reaching the limit of the current codeword size (e.g. 9 -> 10 bits). But the new range only gets 50% used right after increasing by 1 bit, with slow filling of the range.

Is some existing algorithm adressing this? AC, RC, ANS come to my mind here. Anything else?