As we approach the year’s end, it’s clear to see an interesting musical year is almost in the history books. Part of the historic year had to do with digital sales. Back in April, Nielsen projected digital track sales to break the 1 billion mark for 2008. As of December 14, the 1 billion mark has already been broken, proving the projection accurate.

This year, the Top 200 digital songs accounted for about 17 percent of all track sales, equivalent to 171 million. Part of that certainly had to do with Leona Lewis‘ break out hit “Bleeding Love,” which was the highest selling digital song of the year, topping more than 3 million sales for the year.

Lil Wayne‘s chart topping Carter III [click to read] will definitely lead the way in terms of CD sales, but the highest digital sales may go to Coldplay for their new album Viva La Vida, according to iTunes‘ list. Jack Johnson‘s Sleep Through the Static and the Juno soundtrack end the year in the second and third place for digital album sales while Weezy rounds out the fourth spot.

In terms of songs, the aforementioned Lewis leads the way, but Hip Hop and R&B acts follow closely behind. Flo Rida‘s “Low” is only in third place, while Lil Wayne lands in sixth with “Lollipop.” Rihanna has two slots in the top 10 with “Disturbia” and “Don’t Stop the Music” going in at five and ten respectively.

With the year ending, this is just another example of improvement shown in digital sales, which is projected to increase next year. It has gone up consistently each year and the trend could very well continue.