It's another milestone for Apple: The iPhone maker has overtaken Google as the world's most valuable brand, according to the annual BrandZ rankings by the Millward Brown research unit of British advertising giant WPP. Of course, the methodology behind these rankings isn't as exact as the math behind quarterly earnings reports, but Millward Brown does use consumer research and financial analysis to gauge sentiment for top brands, and uses that information to try to pin down their value. Here, a guide to the ranking, by the numbers:

$153.3 billion
Value of Apple's brand, the number one brand, according to Millward Brown

84 percent
Increase in Apple's brand value from 2010

859 percent
Increase in Apple's brand value since 2006, when the BrandZ rankings started

$322 billion
Market value of Apple, based on the closing price of its stock on Tuesday

$111.5 billion
Value of Google's brand, according to Millward Brown

2 percent
Decrease in Google's BrandZ brand value from 2010

Consecutive years that Google had been the world's most valuable brand in Millward Brown's rankings

Number of the top five brands that are in the tech sector. IBM ranked third, McDonald's fourth, and Microsoft came in fifth.

$37.6 billion
Brand value of

$37.3 billion
Brand value of Walmart, which slipped behind Amazon to become the second most valuable retail brand. But Walmart "still has more than 10 times the sales and more than five times the market capitalization of Amazon," says Jack Neff at Advertising Age.

246 percent
Increase in Facebook's brand value from 2010, making it the "top rising brand," according to the report. Facebook's brand is valued at $19.1 billion, just behind popular diaper brand, Pamper's.

141 percent
Increase in the brand value of Chinese search giant Baidu, which is now tallied at $22.5 billion

Chinese brands in the Top 100

Chinese brands in the Top 10 (China Mobile, a tech firm)

Sources: Millward Brown, Financial Times, Venture Beat, Advertising Age