Being a political leader in a democracy is an inherently tenuous role – elections are won or lost, mandates secured or whittled away. In business, leadership has required an ongoing effort to maintain support; but in recent decades, CEOs have started to experience a similar level of volatility that their political counterparts have long faced. Between 2000 and 2010, the average tenure of a Fortune 500 CEO fell from 9.5 years to 3.5 years – a period of time almost mirroring a single American presidential term. In 2011, nearly 15% of the world’s top CEOs left their jobs, with the turnover rate being highest among the 250 largest companies.