During the same year, legal downloads of individual tracks increased by 45% to 844.2m from sites such as Apple Music Store iTunes and Amazon.com. ITunes became the country's third-largest music retailer. Overall, 50m albums were downloaded last year.
The fall in CD album sales, which have been in decline for years, is only in part because of online file-sharing, but also down to the popularity of DVDs and videogames. The top three albums in the US were: a Christmas album by Josh Groban called 'Noel', which sold around 3.7m copies; followed by Walt Disney Co's 'High School Musical', selling 2.9m; with The Eagles' comeback album 'Long Road Out of Eden' in third selling 2.6m.
In the UK, single track downloads rose by almost 50% last year, from 52.5m in 2006 to 77.6m in 2007, according to the British Phonographic Industry.
During the week between Christmas and New Year, 2.9m tracks were bought online, up 1m on the same week in 2006 and was the largest one-week sales tally in the UK to date.
The number one download was 'X Factor' winner, Leon Jackson's 'When You Believe', followed by last year's winner Leona Lewis with 'Bleeding Love'.
A BPI spokesman said: "Recent years have seen a boost in download sales in the week after Christmas, but this was a larger increase than expected, and sales should continue to grow throughout 2008.
"The enormous choice of music and great value for money, combined with the ease and convenience of downloading, means legal digital music services are becoming increasingly popular with music fans."