According to Soundscan, US digital sales hit a new high for the week of Dec. 22 - 28 with 47.7 million sold. That's an increase of about 126% from the previous week.
Why such an enormous sales increase? People filling up iPods to be given as Christmas gifts for one thing. Redeeming iTunes gift cards received over the holidays is another. Either way, it was a big end of the year for digital music.