BWT-based compressors like bzip2 do best when their inputs have highly repetitive structure. In a JSON file with many repeated keys, the information that `"k` i

BWT-based compressors like bzip2 do best when their inputs have highly repetitive structure. In a JSON file with many repeated keys, the information that `"k` is usually followed by `ey_1": "` is compressed very effectively. For similar reasons, bzip2 tends to outperform gzip on executables-- it can more effectively model the conditional probability of opcode sequences. See http://mattmahoney.net/dc/dce.html#Section_55 http://mattmahoney.net/dc/dce.html#Section_55 for more discussion