Apple has always been tight-lipped on how much information it releases in reference to the iTunes Store, a recent report by Forrester Research appears to point towards plummeting sales of music via the online service.

Forrester believed that credit-card transactions over a 27 month period would offer some insight into what was going on with the iTunes Store, according to the report, since January of this year the monthly revenue has fallen by 65-percent with the average transaction size stumbling by 17-percent.

The research did highlight some interesting details about sales via the iTunes Store, some 3.2 percent of online households bought at least one download, the media transaction being just under $3.