A pair of analyst reports measuring the sales of Apple Computer's iTunes Music Store have offered contradictory on the success, or lack thereof, of the popular digital music service.

Forrester Research -- which recently reported that less than 3% of U.S. online households have bought an iTunes file -- says iTunes sales plummeted 65% for the first half of 2006, based on an analysis of credit card transactions over a 27-month period.

The firm also said the average transaction size fell 17%. The figures don't include sales using gift cards, however.

Piper Jaffray analyst Gene Munster later issued a report, noting that iTunes sales show strong growth on a year-over-year basis. The number of songs per week sold via the iTunes service jumped 78% over last year, with 18.5 million songs sold per week in the January to September timeframe of 2006, compared to 10.4 million per week in the same period last year.

Munster also pointed to the traditional sales spike that occurs after the holidays. In January 2005, iTunes' daily sales average increased 58% sequentially. In Feb. 2006, that figure was 51%. Munster expects another leap again early next year.