Blame it on those end-of-year reports. During the rest of December as well as the first few weeks of January, humanity will be bombarded by various facts, figures, numbers and statistics. For those who love numbers, it is the best time of year – but a nightmare for the numerically impaired.

The new JupiterResearch report about the U.S. music market is one such release. Chock full of numbers, Jupiter’s “U.S. Music Forecast, 2008 to 2013” says digital music sales make up 18 percent of the U.S. market and will reach 41 percent in five years, Reuters reported.

But record company execs shouldn’t break out the bubbly just yet. Like other reports in past years, Jupiter isn’t predicting online download sales will replace declining CD sales anytime soon. Instead, the research company predicts the U.S. music market will drop from $10.2 billion to $9.8 billion by 2013.

One of the more interesting aspects of the report is that many consumers who purchase downloadable tunes also purchase physical CDs.

Specifically, 64 percent who subscribe to online subscription services and 57 percent who download music also purchased CDs in the past year.

And yes, online piracy is still a major problem, as any record label exec can tell you. The Jupiter report isn’t predicting any quick fix for the problem, but it does say that paying for music downloads is increasing in popularity.

Details of the report also indicated that consumers prefer unprotected MP3s to DRM-laden proprietary formats. What’s more, Jupiter says consumers now spend about 60 percent of their total music budgets on digital formats.

But despite all the optimistic numbers for online music, there was one area Jupiter wasn’t too keen on – music on cell phones.

The research company predicted that listening to music on mobile phones would have a limited impact, if any, on music consumerism in the U.S. and would amount to less than $300 million in sales by 2013.