The 2011 Sports Illustrated issue was revealed last night, featuring 25-year-old Russian model, Irina Shayk, on this year's magazine cover.
It is the most profitable single-issue magazine franchise in the world, and a multi-million-dollar business. CNBC.com took a look at how the market performs in years that the magazine cover featured a blonde versus a brunette.
The models' hair color was gauged from the Sports Illustrated website, dating back to 1964.
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48 covers from 1964 until now: