Hutter's contest only goes back to 2006, and is very much not a generalizable progress curve as it's based on a static dump of Wikipedia. You'd want to also use Calgary & Canterbury Corpus results. (Ideally you'd dredge up compressors from the early history of computing, like basic Unix utilities from the '60s or '70s, but then you have the difficulty of actually running them - same issue that bars really good evaluation of "Proebsting's Law".)