Lana has one so far....Born to Die, which is around 5.5 million.

Avril had three:

Let Go (18 million)
UMS (10 million)
TBDT (6 million)

2: The Fame / Monster, which is around 15M & Born This Way, which is at 6.3M.

3: CA, Stripped, and BTB.

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everything she's released

Avril has two.

What The Hell and Girlfriend

Janet has 6 (Control, Rhythm Nation 1814, janet., The Velvet Rope, All for You, Design of a Decade)
Katy has 2 (One of the Boys allegedly, Teenage Dream)
Shania has 4 (The Woman In Me, Come on Over, Up!, Greatest Hits)

Taylor Swift - 6M
Fearless - 9.5M
Speak Now - 6M
Red - 6.5M
1989 - 8.1M

Madonna:

Her debut(10M)
Like a Virgin(21M)
True Blue(23M)
Who's That Girl(5.2M)
You Can Dance(5.8M)
Like a Prayer(14M)
The Immaculate Collection(28.5M)
I am Breathless OST(7M)
Erotica(6.8M)
Bedtime Stories(8M)
Something to Remember(10M)
Evita Soundtrack(6.5M)
Ray of Light(16M)
Music(11M)
GHV2(5.5M)
COADF(10M)

16 for Madonna

Out of 22 studio albums&compilations&soundtracks

Lana:

Born to Die(6,033M)

Rih,Katy,Bey and Brit are already done.

...Baby One More Time
Oops!... I Did It Again
Britney
In The Zone
Greatest Hits: My Prerogative

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Avril

Let Go: 17M
Under My Skin: 10M
The Best Damn Thing: 6.5M

IKR?

Mariah has 10.

'Mariah Carey' (1990) 14 million
'Emotions' (1991) 8 million
'MTV Unplugged' (1992) 5,5 million
'Music Box' (1993) 27 million
'Merry Christmas' (1994) 13 million
'Daydream' (1995) 21 million
'Butterfly' (1997) 11 million
'Number Ones' (1998) 15 million
'Rainbow' (1999) 8 million
'The Emancipation Of Mimi' (2005) 10 million

And Bey has 3.Not 4

'Dangerously In Love' (2003) 10,0 million
'B'day' (2006) 6,5 million
'I Am... Sasha Fierce' (2008) 7,5 million

The Fame
The Fame Monster EP
Born This Way

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