It's not clear if iTunes Radio has hurt U.S. track sales since its Sept. 18th launch. One thing is clear, however: aggregate track sales haven't been helped by the arrival of Apple's Internet radio service.

A recent dip in track sales happens to coincide with the launch of iTunes Radio. Weekly track sales averaged 20.28 million from September 16th through November 3rd, according to Nielsen SoundScan. That average is about 13% below the weekly average of 22.95 million from June 24th to September 15th. Weekly sales never fell below 22 million in June or August. Nor did weekly track sales fall below 22 million in the weeks before iTunes Radio launched. But when iTunes Radio debuted, weekly sales immediately dipped to 21.9 million, then to 21.2 million. Since then, there were four consecutive weeks under 20 million, two weeks with sales above 20 million (20.4 million and 20.6 million) and, in the most recent week, another sub-20 million week.

 

Track sales haven't been the same since the week ending June 23rd. That was week Robin Thicke's "Blurred Lines" peaked with 424,000 units sold. Daft Punk's "Get Lucky" also reached its peak that week with 202,000 units sold. Total track sales were 26.51 million that week. Sales the next two weeks were 25.2 million and 24.4 million. Sales over the next ten weeks -- up to the launch of iTunes Radio -- averaged 22.5 million and surpassed 23 million just once.

The downward trend started early in 2013. Track sales experienced their normal, post-Christmas decline in the first weeks of the year. The Grammy Awards resulted in a spike to 29.43 million from 27.32 million a week earlier. Other than a two-week period spanning March and April, track sales slid after the Gramm Awards and until "Blurred Lines" and "Get Lucky" peaked.

iTunes Radio has got off to a strong start. Twenty million U.S. consumers tried iTunes Radio in its first 34 days. A recent survey by Mark Kassof & Co says 18% of consumers age 13 to 34 "love" iTunes Radio, well below the 39% that "love" Pandora but commendable for such a young service.

A number of factors could be at play in this year's downward trend in track sales, namely the maturation of the digital download and the rise of subscription services. And, again, weekly sales were on a downward trajectory before iTunes Radio launched. For perspective, last week's track sales were 27% lower than the week before the Grammy Awards.

There exists a long-held belief that radio -- whether broadcast or Internet -- is additive to music sales. That is to say, radio is good for sales. It may act as a substitute for some music purchases, but radio is a valuable discovery mechanism that has a net positive impact on sales. That belief may be accurate, but it doesn't explain what has happened to track sales over the last nine weeks.