I'm guessing that the sheer amount of PVs also has to do with it.
1998 - poker face, YOU, Trust, For My Dear.., Depend on You
1999 - WHATEVER, LOVE~destiny~, TO BE, Boys&Girls, appears, kanariya
2000 - Fly high, vogue, Far away, SEASONS, SURREAL, M
2001 - evolution, Endless sorrow, Dearest
2002 - Daybreak, Free&Easy, Connected, Voyage, Real me
2003 - RAINBOW, ourselves, Greatful days, HANABI~episode II~, forgiveness, No way to say, Because of You, ANGEL'S SONG
2004 - Moments, INSPIRE, GAME, CAROLS, walking proud, About You, Humming 7/4
2005 - STEP you, is this LOVE?, fairyland, alterna, HEAVEN, Bold&Delicious, Pride, Ladies Night, rainy day
2006 - Startin', Born to Be.., BLUE BIRD, Beautiful Fighters
In recent years, she's had SO many..