The leading DRM digital download service, Apple's iTunes, has experienced a collapse in sales revenues this year according to analyst company Forrester Research.

Secretive Apple doesn't break out revenues from iTunes, but Forrester conducted an analysis of credit card transactions over a 27-month period. And this year's numbers aren't good.

While the iTunes service saw healthy growth for much of the period, since January the monthly revenue has fallen by 65 per cent, with the average transaction size falling 17 per cent. The previous spring's rebound wasn't repeated this year.

And it isn't just Apple's problem. Nielsen Soundscan has grimmer news for prospective digital download services, indicating three consecutive quarters of flat or declining revenues for the sector as a whole.

Speaking to The Register, Forrester analyst Josh Bernoff warned against extrapolating too much from the figures.

It may reflect a seasonal bounce that hasn't yet manifested itself. However, it might not.

"There's no indication of enormous growth coming," he told us. "When you look at this alongside the SoundScan numbers, you may ask 'Where's the part were we're supposed to get excited?'."

The ominous trend comes despite healthy growth for digital music players - iPod sales quadrupled in the period monitored by Forrester - and Apple's growing inventory - the company has added videos and movies to its established inventory of music downloads and audiobooks.

Read more here: The Register