According to the 2014 edition of Edison's annual audio report "The Infinite Dial", Pandora remains the most popular music streaming service in the United States.
Follow up:Thirty one percent of those polled for the report stated to have used Pandora within the last month. That puts the ad-supported online radio healthily in front of iHeartRadio and iTunes Radio which were used by 9 and 8 percent of the respondents, respectively. Ranked fourth, Spotify was the first on-demand streaming service on the list with an adoption rate of 6 percent.
You will find more statistics at Statista