Is there a logic for deciding when to employ furigana?


I'm vaguely aware that the usage of _furigana_ is based on the intended target
audience. The younger or less likely literate the target audience the more
_furigana_ are employed. But is there a system to decide which words receive
_furigana_ and which don't? In intermediate novels I find it not unusual to
find _furigana_ on words that were printed without just a few pages earlier.
Is this done because somebody decided that that word/reading is less likely to
be known in that context, or is it pretty _"tekitō"_?




I can't answer on the particular case of a word that would receive furigana
_after_ not receiving it earlier (the opposite, however, is naturally quite
common): assuming the words are rigorously identical and identically read both
times, this sounds more like an oversight than anything.

As for the general rules of adding furigana, they are pretty straightforward,
depending on what kanji level can be expected from the reader.

One should probably separate:

  * Readings targeting children and young adults (about anybody at High School age or under) have very fluid rules, as far as I can tell. _Overall_ , they will try and follow the regular Japanese school curriculum, which is very specific about which kanji must be mastered by when. But since their target demographic itself might not be all that exact, they will probably err on the side of caution and annotate all **non-kyouiku kanji**.

  * Regular readings: newspapers, novels, manga for adults (adult- _age_ , not adult- _themed_ ) etc. will generally put furigana only for highly irregular readings and kanji that are **outside of the jouyou set**. I believe adding furigana to non-jouyou kanji is even a requirement by law for newspapers (but I cannot find a source for this just now). Of course, the socio-professional status of the intended audience will probably play a role in how generous with extraneous furigana they are (e.g. cheap weekly magazines etc.), but I noticed such materials just tend to skip the kanji and go straight to kana when needed...

It must be said that the strictness in kanji requirement (compensated by the
use of furigana) has dramatically decreased over the past 30-40 years: to
convince yourself, just compare a copy of any 70s-era manga (e.g. Tezuka
Osamu's _Black Jack_ ) with modern day mangas targeting the same demographic
("shounen" - young adult): the latter have furigana all over (anything beyond
Jr High School level, essentially), while the former barely bothers putting
furigana on even the most obscure proper noun kanji (let alone anywhere else).

**Edit:** there's been much debate in the answer below, regarding the
existence of clearly-defined official guidelines (as opposed to obscure in-
house rules). _At least for newspapers_ , I stand my ground and reiterate:
**Jouyou kanji** is the **officially agreed** base set of kanji to be used in
Japanese publications, with some modifications clearly defined and agreed upon
by the association of Japanese newspaper editors (source: [Wikipedia
Jp](http://ja.wikipedia.org/wiki/%E6%96%B0%E8%81%9E%E6%BC%A2%E5%AD%97%E8%A1%A8)).
One could argue that there is yet another small decision-making step from
"kanji that people aren't expected to know" to "kanji that need to be
furiganised", but frankly, I'm not going there.




I can't answer on the particular case of a word that would receive furigana
_after_ not receiving it earlier (the opposite, however, is naturally quite
common): assuming the words are rigorously identical and identically read both
times, this sounds more like an oversight than anything.

As for the general rules of adding furigana, they are pretty straightforward,
depending on what kanji level can be expected from the reader.

One should probably separate:

  * Readings targeting children and young adults (about anybody at High School age or under) have very fluid rules, as far as I can tell. _Overall_ , they will try and follow the regular Japanese school curriculum, which is very specific about which kanji must be mastered by when. But since their target demographic itself might not be all that exact, they will probably err on the side of caution and annotate all **non-kyouiku kanji**.

  * Regular readings: newspapers, novels, manga for adults (adult- _age_ , not adult- _themed_ ) etc. will generally put furigana only for highly irregular readings and kanji that are **outside of the jouyou set**. I believe adding furigana to non-jouyou kanji is even a requirement by law for newspapers (but I cannot find a source for this just now). Of course, the socio-professional status of the intended audience will probably play a role in how generous with extraneous furigana they are (e.g. cheap weekly magazines etc.), but I noticed such materials just tend to skip the kanji and go straight to kana when needed...

It must be said that the strictness in kanji requirement (compensated by the
use of furigana) has dramatically decreased over the past 30-40 years: to
convince yourself, just compare a copy of any 70s-era manga (e.g. Tezuka
Osamu's _Black Jack_ ) with modern day mangas targeting the same demographic
("shounen" - young adult): the latter have furigana all over (anything beyond
Jr High School level, essentially), while the former barely bothers putting
furigana on even the most obscure proper noun kanji (let alone anywhere else).

**Edit:** there's been much debate in the answer below, regarding the
existence of clearly-defined official guidelines (as opposed to obscure in-
house rules). _At least for newspapers_ , I stand my ground and reiterate:
**Jouyou kanji** is the **officially agreed** base set of kanji to be used in
Japanese publications, with some modifications clearly defined and agreed upon
by the association of Japanese newspaper editors (source: [Wikipedia
Jp](http://ja.wikipedia.org/wiki/%E6%96%B0%E8%81%9E%E6%BC%A2%E5%AD%97%E8%A1%A8)).
One could argue that there is yet another small decision-making step from
"kanji that people aren't expected to know" to "kanji that need to be
furiganised", but frankly, I'm not going there.

