Looks like streaming services such as Pandora and Spotify are hitting digital music sales where it hurts. Billboard reports digital track sales have dropped 5.7 percent to 1.34 billion units for the first time in 2013 since iTunes Store opened 10 years before. Album sales also dropped 0.1 percent to 117.6 million. Streaming services that provide unlimited seem to entice listeners to subscribe to them instead of buying albums that cost roughly the same price.