A company's worth is rarely equal to the sum of its assets. In fact, most corporations hold intangible value. An important case in point: brand image. Research shows that brand power can account for as much as 10% of the change in a company's stock price—up or down. The past year has made all too clear that a company's image is no guarantee of future performance. The following publicly traded brands are the "healthiest" right now, as measured by ("YouGov's BrandIndex"), which tracks consumers' perceptions across six categories by polling 5,000 people each weekday. YouGov, a polling firm, scores each category from -100 to +100, then averages the grades for each company to come up with its BrandIndex score.