From Oricon BiZ:
Values are in millions of yen.
01. Arashi
02. Tohoshinki
03. AKB48
04. Ikimonogakari
05. EXILE
06. Kanjani8
07. Hamasaki Ayumi
08. KAT-TUN
09. Nishino Kana
10. Koda Kumi
Ayu sold about 2.83 billion yen worth of CDs/DVDs this year. 678 million yen came from singles, 1.3 billion yen from albums, and 866 million yen from live DVD sales.
Ayu placed 7th for the year. Arashi was 1st with a whopping 16.8 billion yen in sales! I think she counts as the top solo female artist if Ikimonogakari is counted as a female-led band. Not sure. Pretty impressive considering she's been around the longest out of most of these acts. (Not sure about EXILE though.)
Source -
http://biz-m.oricon.co.jp/news/data/544.shtml
Past rankings:
2009 - 9th - 3.436 billion
2008 - 2nd - 7.188 billion
2007 - 2nd - 7.057 billion
2006 - 5th - 6.893 billion
2005 - 4th - 6.908 billion
2004 - 5th - 5.4 billion
2003 - 1st - 10.5 billion
2002 - 2nd - 11.5 billion
2001 - 1st - 24.5 billion
2000 - 1st - 21.7 billion
1999 - 5th - 19.7 billion