Americans are falling out of love with downloading music.

Over the past five quarters, the average number of songs downloaded per MP3 player (search) owned has dropped an astounding 41.4 percent, according to industry data contained in a recent report.

U.S. MP3 owners are downloading an average of just 13.6 songs per year as of Sept. 30, off from 23.2 songs a year earlier, according to the report, by Fulcrum Global Partners (search) analyst Richard Greenfield.

Most reports on digital music sales have spotlighted the fantastic 150 percent growth in total downloads.

But the Greenfield report explains that the nearly fourfold jump in the number of MP3 players in circulation, to about 23 million, over that same period means folks are buying far less music per player.

For an industry so focused on weekly numbers, the decline in online buying per-user so early in the digital music life cycle should be cause for concern.

"Weekly digital-downloads have not increased rapidly throughout 2005," wrote Greenfield, who questioned whether the current rate of digital sales growth will be enough to offset music's still-declining physical sales.

Russ Crupnik, with NPD Group (search), understands the decline. He said "over 90 percent of what people put on their players is from a rip from their own or a friend's CD."

And no one expects that to change any time soon.