Wozniacki will travel to the WTA's season finale for the fourth time, having qualified as one of the elite eight three times before - 2009 (reaching the semifinals before falling to Serena Williams), 2010 (reaching the final before falling to Kim Clijsters) and 2011 (falling in the round robin stage).
The Dane has made the quarterfinals or better 10 times this season, including one title (Luxembourg), another final (Indian Wells) and four semifinals (Dubai, Eastbourne, New Haven and Tokyo).
Stephens is heading to the WTA's season finale for the first time in her career, as an alternate or as part of the elite eight - in fact she had never even been ranked in the Top 30 before this year began.
The American's breakthrough season has included some phenomenal results at the Grand Slams - she went 15-4 at the majors, making the fourth round or better at all four (highlighted by the semifinals of the Australian Open and quarterfinals of Wimbledon). In regular WTA events she made one semifinal (Hobart) and five quarterfinals (including Premier-level events at Brisbane, Brussels and New Haven).
The Top 8 singles players and Top 4 doubles teams will compete in Istanbul for a record-setting $6 million prize money purse and the most prestigious title on the WTA calendar after the Grand Slams.
This year's elite eight is Serena Williams, Victoria Azarenka, Agnieszka Radwanska, Li Na, Sara Errani, Petra Kvitova, Jelena Jankovic and Angelique Kerber. The four doubles teams are Errani and Roberta Vinci, Hsieh Su-Wei and Peng Shuai, Nadia Petrova and Katarina Srebotnik, and Ekaterina Makarova and Elena Vesnina. Errani is the only player taking part in both singles and doubles.
Following two successful, record-breaking editions, Istanbul hosts the WTA Championships for the third and final year in 2013. In 2012, the tournament attracted more than 73,000 fans during six days of competition, the highest attendance at the year-end event since 2000. Broadcast coverage reached 167 countries, and the overall hours produced increased 25 percent, including live matches, match replays and highlights. Nearly 42 million fans followed the on-court and behind-the-scenes action via WTA social media and digital platforms, and it was a record-setting week for the official WTA website that week, with approximately 4.8 million page impressions and nearly 500,000 unique visitors.