Do u.s. firms have the best corporate governance?

"We compare the governance of foreign firms to the governance of similar U.S. firms. Using an index of firm governance attributes, we find that, on average, foreign firms have worse governance than matching U.S. firms. Roughly 8% of foreign firms have better governance than comparable U.S. firms. The majority of these firms are either in the U.K. or in Canada. When we define a firm's governance gap as the difference between the quality of its governance and the governance of a comparable U.S. firm, we find that the value of foreign firms increases with the governance gap. This result suggests that firms are rewarded by the markets for having better governance than their U.S. peers. It is therefore not the case that foreign firms are better off simply mimicking the governance of comparable U.S. firms. Among the individual governance attributes considered, we find that firms with board and audit committee independence are valued more. In contrast, other attributes, such as the separation of the chairman of the board and of the CEO functions, do not appear to be associated with higher shareholder wealth"--National Bureau of Economic Research web site.