Please answer a question about the following article about Beyoncé:

Forbes magazine began reporting on Beyoncé's earnings in 2008, calculating that the $80 million earned between June 2007 to June 2008, for her music, tour, films and clothing line made her the world's best-paid music personality at the time, above Madonna and Celine Dion. They placed her fourth on the Celebrity 100 list in 2009 and ninth on the "Most Powerful Women in the World" list in 2010. The following year, Forbes placed her eighth on the "Best-Paid Celebrities Under 30" list, having earned $35 million in the past year for her clothing line and endorsement deals. In 2012, Forbes placed Beyoncé at number 16 on the Celebrity 100 list, twelve places lower than three years ago yet still having earned $40 million in the past year for her album 4, clothing line and endorsement deals. In the same year, Beyoncé and Jay Z placed at number one on the "World's Highest-Paid Celebrity Couples", for collectively earning $78 million. The couple made it into the previous year's Guinness World Records as the "highest-earning power couple" for collectively earning $122 million in 2009. For the years 2009 to 2011, Beyoncé earned an average of $70 million per year, and earned $40 million in 2012. In 2013, Beyoncé's endorsements of Pepsi and H&M made her and Jay Z the world's first billion dollar couple in the music industry. That year, Beyoncé was published as the fourth most-powerful celebrity in the Forbes rankings. MTV estimated that by the end of 2014, Beyoncé would become the highest-paid black musician in history; she succeeded to do so in April 2014. In June 2014, Beyoncé ranked at #1 on the Forbes Celebrity 100 list, earning an estimated $115 million throughout June 2013 – June 2014. This in turn was the first time she had topped the Celebrity 100 list as well as being her highest yearly earnings to date. As of May 2015, her net worth is estimated to be $250 million.

When did Jay Z and Beyoncé become the first music couple worth over a billion dollars?
2013