However, following revisions to the methodology used to compile the published figures, 2004-05 is the earliest year for which figures are comparable on exactly the same basis.
Fodd bynnag, yn dilyn diwygio’r fethodoleg a ddefnyddir i baratoi y ffigurau a gyhoeddwyd, 2004-05 yw y flwyddyn gynharaf i gymharu ffigurau ar union yr un sail.