(FT) -- Apple has overtaken Google to become the world's most valuable brand with an estimated brand value of more than $153bn, according to new rankings published on Monday. For the last four years, Google has dominated the BrandZ Top100 ranking of the most valuable global brands, compiled by Millward Brown, a subsidiary of advertising company WPP. The ranking covers everything from cars to clothing and banks to telecoms providers. Thanks to the success of the iPad tablet and iPhone mobile -- among both consumers and corporations -- Apple's brand value has surged in the last year to overtake that of the search engine company. Apple has increased its brand value by $137bn, or 859 per cent, since 2006 when the BrandZ rankings were launched. The brand valuation compares with Apple's stock market capitalisation of $319.4bn, which is almost five times higher than in 2006. Google's market capitalisation is $172.4bn. The BrandZ index calculates brand value on a number of factors, including an estimate of the brand's contribution to earnings, valuation of intangible assets, measures of customer perception and an estimate of growth potential. Peter Walshe, global BrandZ director at Millward Brown, said Apple's success reflected the fact that its products were not only highly desired by consumers but also seen by companies as useful. "The anecdotal evidence is that if employees are given the choice of two similar jobs they opt for the one with better technology for its employees -- for example an iPad," Mr Walshe said. Apple, he added, had also succeeded in emulating luxury goods brands, in that making its products more expensive had increased their desirability.