It doesn't really matter since most document formats already use compression. No matter what encoding you use, the amount of entropy is the same. So UTF-8 usual

It doesn't really matter since most document formats already use compression. No matter what encoding you use, the amount of entropy is the same. So UTF-8 usually compresses better than 2-byte encodings for CJK languages. This nearly compensates for the increased size. Example: The Korean text of the Universal Declaration of Human Rights [1] is 8.1KB in EUC-KR and 11.2KB in UTF-8. When compressed with bzip2, it's only 3.1KB and 3.2KB, respectively. I assume Japanese would behave similarly. [1] http://www.ohchr.org/EN/UDHR/Pages/Language.aspx?LangID=kkn http://www.ohchr.org/EN/UDHR/Pages/Language.aspx?LangID=kkn