South Korean single sales
Hold It Against Me - 678,854 (2011)
S&M (Remix) - 596,307 (2011, 2012, 2013, 2015)
3 - 569,569 (2010, 2011, 2012)
I Wanna Go - 559,470 (2011, 2012)
TTWE - 395,600 (2011, 2012) (including 74,749 for the Femme Fatale Remix and 9,550 for the Culture Shock Remix)
Scream & Shout - 152,651 (2012, 2013, 2014, 2016)
Ooh La La - 73,681 (2013)
Criminal - 71,412 (2011, 2012)
Work Bitch - 46,674 (2013)
Perfume - 31,849 (2013)
Pretty Girls - 28,589 (2015)
Toxic - 26,895 (2012, 2014)
Lucky - 18,046 (2012, 2013)
Make Me... - 8,138 (2016)
Oops!... I Did It Again - 7,536 (2011, 2012, 2016)
Scary - 220,356 (2011)
My Only Wish - 117,171 (2011, 2012, 2013, 2014, 2015, 2016)
Up 'n' Down - 116,030 (2011)
It Should Be Easy - 79,479 (2013, 2014)
Gasoline - 46,556 (2011)
Big Fat Bass - 41,030 (2011)
Brightest Morning Star - 36,107 (2013, 2014)
How I Roll - 31,291 (2011)
Inside Out - 31,203 (2011)
Tom's Diner - 19,166 (2015)
(Drop Dead) Beautiful - 17,328 (2011)
Trouble for Me - 16,208 (2011)
Seal It with a Kiss - 15,142 (2011)
Trip to Your Heart - 13,863 (2011)
I Will Be There - 12,540 (2012)
Tik Tik Boom - 11,472 (2013)
Til It's Gone - 9,934 (2013)
Body Ache - 8,303 (2013)
I Will Still Love You - 3,594 (2012)
Alien - 3,212 (2013)
Don't Cry - 2,735 (2013)
Chillin' with You - 2,652 (2013)
Passenger - 2,573 (2013)
Brave New Girl - 1,753 (2012)
Selfish - 1,229 (2011)
Don't Keep Me Waiting - 1,001 (2011)
He About to Lose Me - 997 (2011)
Private Show - 720 (2016)
Now That I Found You - 647 (2014)
Unfortunately, Gaon removed all numbers for 2010 (we only know 3 sold 506,000 copies that year because people saved the YEC). But she had several songs charting that year (3, If U Seek Amy, Circus, Womanizer, Toxic, Radar, Lucky and My Only Wish).
My estimations for 2010:
If U Seek Amy - 45,000
My Only Wish - 35,000
Circus - 20,000
Womanizer - 15,000
Toxic - 15,000
Radar - 5,000
If U Seek Amy was #246 on the 2010 YEC. #150 sold 88k and #200 sold 67k so there was only a 20k difference. Assuming it's the same for #200-#246 = around 45,000.
Gaon also removed sales for the first two months of 2011 but she also had several songs charting
January 2011:
#1 Hold It Against Me
#98 Circus
#136 3
#289 If U Seek Amy
#358 Toxic
February 2011:
#4 Hold It Against Me
#271 Circus
For January and February 2011, I estimate Circus sold over 20,000, 3 around 10,000, IUSA around 5,000 and Toxic around 3,000.
tl:dr version: Up to date estimated sales:
Hold It Against Me - 685,000
S&M (Remix) - 610,000
3 - 600,000
I Wanna Go - 565,000
Till The World Ends - 400,000
Scream & Shout - 155,000
Ooh La La: 75,000
Criminal - 75,000
If U Seek Amy - 55,000
Toxic - 45,000
Circus - 45,000
Perfume - 35,000
Work Bitch: 50,000
Pretty Girls: 30,000
Lucky - 20,000
Womanizer - 20,000
Oops!...I Did It Again - 10,000
Make Me... - 10,000
Radar - 5,000
Album Tracks - 950,000 (includes around 155,000 for My Only Wish)
Total: 4,440,000 tracks sold in South Korea since 2010
MAKE ME
