Kindle Already Over 15 Percent of Amazon’s Business, Analyst Estimates

We’ve seen a lot of extremely high estimates for Kindle revenues recently: a Citigroup report earlier this week projected that Kindle would bring in $3.2 billion in revenue this year, about 8 percent of Amazon’s $34.2 billion business, and would make up 10 percent of the company’s revenue next year.

But a new report is even more optimistic: Caris & Co. analyst Sandeep Aggarwal estimated today that Kindle will rake in over $5.48 billion this year, and $8.64 billion in 2012.

Those numbers are revised upward from an estimate Aggarwal made just a month ago. The 2012 figures are about 8 percent higher than he estimated in May. Aggarwal increased his estimates partly due to the fact that Amazon (NSDQ: AMZN) reported on May 19 that it’s sold three times as many e-books so far in 2011 as it did during the same period in 2010, and that Amazon UK is now selling more e-books than hardcovers, at a rate of about 2 to 1.

Amazon has never released Kindle sales numbers, a fact that Aggarwal attributes to the sheer magnitude of the Kindle business.

May was a big month for e-reader announcements, with Barnes & Noble and Kobo both launching new devices. (See our comparison of the latest e-readers.) But Kindle’s market share is still estimated at over 60 percent.