generate questions: In 2004, worldwide sales of audio CDs, CD-ROMs and CD-Rs reached about 30 billion discs. By 2007, 200 billion CDs had been sold worldwide. CDs are increasingly being replaced by other forms of digital storage and distribution, with the result that audio CD sales rates in the U.S. have dropped about 50% from their peak; however, they remain one of the primary distribution methods for the music industry. In 2014, revenues from digital music services matched those from physical format sales for the first time.
In what year were digital and physical music sales the same? {sep_token} How many CDs had been distrubuted worldwide by 2007? {sep_token} In 2004 how many CDs had been sold around the world? {sep_token} What percent decrease did audio CD sales experience? {sep_token} What has caused a decrease in CD sales? {sep_token} In 2004 how many CDs had been sold around the world? {sep_token} How many CDs had been distrubuted around the world by 2007? {sep_token} What has caused a decrease in CD sales? {sep_token}