Two cheers for US corporate governance. In a survey of chief executive turnover, Booz & Co finds companies in the US are increasingly separating the chairman and CEO roles, bringing it belatedly into line with other developed countries. Fewer than one in five new American CEOs now start out holding the chairman’s post too, down from half in 2001. However, more than half of CEOs currently start as “apprentices” – their predecessor having become chairman.

Separating the roles guards against concentration of power, ensuring the chairman can assess strategy and management dispassionately. But CEOs “stepping up” to chairman is a trickier issue. The UK’s governance code, for example, stipulates that a CEO should go on to chair the company only in exceptional circumstances and after consulting shareholders. That provision is, however, being questioned. A study of Europe’s biggest 25 banks by Nestor Advisors, a corporate governance consultancy, found box-ticking was little guide to which banks pulled through the crisis best. In fact, banks chaired by finance industry specialists clearly performed better than those led by non-expert chairmen. Three outperformers split the chairman and CEO roles in 2007, while some retained a former CEO as chairman.