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Measuring a brand's worth is an imprecise art. Apple has nevertheless been deemed the world's most valuable.

At $153 billion, according to a new survey, it accounts for about half the company's market capitalisation and nearly 10 times its estimated value five years ago.

Tech companies also populate the top ranks. There are good reasons they dominate the list - and why they're prone to big swings in value.

The survey, by a subsidiary of WPP, estimated the earnings resulting from big brands and attempted to put a multiple on them to account for future growth.

The result is a tech-heavy list. Google, at $111 billion, ranks second, IBM is third and Microsoft fifth.

Al Jazeera's Rob Reynolds has the story from Los Angeles.

Source: Al Jazeera