Serena Williams, Karolina Pliskova and Victoria Azarenka were among those leading the WTA in various statistical categories in 2016.
WTA Staff

It was a record-breaking year in many statistical categories on the WTA, with a lot of superstars leading the way - for instance Serena Williams in various serving and Victoria Azarenka in various returning categories. Who else headed the lists? Here are the leaders in a variety of stats for each year since the WTA started tracking data for all WTA and Grand Slam main draw matches in 2008:

Aces
2008: Nadia Petrova: 353
2009: Serena Williams: 381
2010: Nadia Petrova: 306
2011: Marion Bartoli: 270
2012: Serena Williams: 484
2013: Serena Williams: 480
2014: Serena Williams: 452
2015: Karolina Pliskova: 517
2016: Karolina Pliskova: 530
Note: Pliskova led the category for the second straight time.

First Serve Percentage
2008: Camille Pin: 74.8%
2009: Monica Niculescu: 72.3%
2010: Sara Errani: 75.8%
2011: Sara Errani: 76.8%
2012: Sara Errani: 76.3%
2013: Sara Errani: 82.8%
2014: Sara Errani: 81.6%
2015: Sara Errani: 82.8%
2016: Sara Errani: 84.8%
Note: Errani led the category for the seventh straight year and set a record for highest percentage.

First Serve Points Won
2008: Anna-Lena Groenefeld: 76.0%
2009: Serena Williams: 73.5%
2010: Serena Williams: 75.3%
2011: Serena Williams: 76.7%
2012: Serena Williams: 77.8%
2013: Serena Williams: 74.7%
2014: CoCo Vandeweghe: 75.2%
2015: Serena Williams: 75.9%
2016: Serena Williams: 75.7%
Note: Williams led the category for the seventh year.

Points Won Returning First Serve
2008: Greta Arn: 44.2%
2009: Dinara Safina: 43.1%
2010: Anabel Medina Garrigues: 42.4%
2011: Maria Sharapova: 43.8%
2012: Sara Errani: 44.7%
2013: Yvonne Meusburger: 46.1%
2014: Monica Niculescu: 43.8%
2015: Sara Errani: 44.3%
2016: Agnieszka Radwanska: 42.6%
Note: Radwanska became the ninth different woman to lead this stat.

Points Won Returning Second Serve
2008: Victoria Azarenka: 61.8%
2009: Victoria Azarenka: 62.1%
2010: Kim Clijsters: 62.7%
2011: Kim Clijsters: 61.6%
2012: Victoria Azarenka: 63.8%
2013: Victoria Azarenka: 64.7%
2014: Chanelle Scheepers: 59.9%
2015: Sara Errani: 61.8%
2016: Victoria Azarenka: 66.6%
Note: Azarenka led the category for the fifth time and set a record for highest percentage.

Service Games Won
2008: Serena Williams: 79.4%
2009: Serena Williams: 77.6%
2010: Serena Williams: 81.4%
2011: Serena Williams: 85.4%
2012: Serena Williams: 87.5%
2013: Serena Williams: 84.1%
2014: Serena Williams: 80.9%
2015: Serena Williams: 81.1%
2016: Serena Williams: 83.8%
Note: Williams led the category for the ninth straight year.

Break Points Saved
2008: Justine Henin: 65.1%
2009: Samantha Stosur: 63.2%
2010: Serena Williams: 65.9%
2011: Serena Williams: 67.5%
2012: Serena Williams: 67.8%
2013: Serena Williams: 64.8%
2014: Lucie Safarova: 76.8%
2015: Karolina Pliskova: 64.3%
2016: Victoria Azarenka: 66.4%
Note: Azarenka led the category for the first year.

Return Games Won
2008: Jelena Jankovic: 48.4%
2009: Victoria Azarenka: 49.5%
2010: Elena Dementieva: 48.3%
2011: Maria Sharapova: 49.7%
2012: Victoria Azarenka: 52.5%
2013: Victoria Azarenka: 54.8%
2014: Monica Niculescu: 49.2%
2015: Sara Errani: 51.9%
2016: Victoria Azarenka: 54.7%
Note: Azarenka led the category for the fouth time and nearly matched her own record for highest percentage.