Taylor Swift - "We Are Never Ever Getting Back Together" - 623,000 (2012)
Katy Perry - "Roar" - 557,000 (2013)
Lady Gaga - "Born This Way" - 448,000 (2011)
Taylor Swift - I Knew You Were Trouble - 416k (2012)
Britney Spears - "Hold It Against Me" - 411,000 (2011)
Katy Perry - "Part of Me" - 411,000 (2012)
Taylor Swift - Today was a Fairytale - 325k (2010)
Taylor Swift - Red - 312k (2012)
Taylor Swift - Begin Again - 299k (2012)
Taylor Swift - "Mine" - 297,000 (2010)
Katy Perry - "California Gurls" (feat Snoop Dogg) - 294,000 (2010)
Taylor and Katy are pretty much the digital queens.
Taylor's top song edges Katy's top song, Taylor's 2nd song edges Katy's 2nd, and Taylor's 3rd/4th/5th/6th songs edge Katy's 3rd.
I wonder if Taylor will break Flo Rida's record this era (or at least her own). If not, with digital sales declining I can only see ADELE & Katy's next lead singles with a minor shot.
Besides those 11 I listed (besides RED which was blocked by 1D), #1 HDS debuts this decade (aka 2010):
What’s My Name/Rihanna 235, Back to December/Taylor 242, Only Girl/Rihanna 249, We R Who We R/Ke$ha 280
Last decade: Don’t Forget About Us/Mariah 39, Beautiful Liar/Shakira & Beyonce 150, SOS/Rihanna 170, Gimme More/Britney 179, If I Were a Boy/Beyonce 190
Single Ladies/Beyonce 204, Circus/Britney 212, Party in the USA/MIley 226, 3/Britney 255, Take a Bow/Rihanna & Hips Don’t Lie/Shakira 267
Umbrella/Rihanna 277, My Life Would Suck Without You/Kelly 280, Womanizer/Britney & Touch My Body /Mariah 286