NEW YORK The economic downturn is taking its toll on the value of the top global brands, according to a new study being released today by London-based Brand Finance. The study also reports a reordering of the top-five brands with Wal-Mart displacing Coca-Cola as the top global brand.According to the report, during the first nine months of the year, troubles in the global economy have caused the cumulative brand value of the top 100 global brands to decrease by 4.2 percent or $67 billion.Many factors contribute to the brand valuation formula used by the firm, said company CEO David Haigh, "but it's driven by projections of future sales and profits." Other factors include an evaluation of brands' current positioning, cost of capital and certain brand equity metrics such as awareness, preference, strength of image and product quality, among other considerations.Wal-Mart climbed from the No. 4 ranking to the top spot while Coke fell to second place. The big-box store, said Haigh, "is the kind of company people go to when they start tightening their belts. In a way they live on the discomfort of other brands," which consumers perceive as something they can live without when times get tough.Microsoft, which had been No. 2, slipped to the third spot on the Brand Finance list, while IBM climbed a notch to fourth and Google fell from third to fifth. By contrast, Coke retained its top-ranked position in a brand value survey by Interbrand, released last week. IBM was ranked second and Microsoft was third.