Is it better to be an early bird or a night owl?

Rare is the chief executive who extols the virtues of a lie-in. Tim Cook, boss of Apple, maker of the iPhone, wakes between 4am and 5am. So does Bob Iger, his counterpart at Disney, a media giant. According to one survey, two-thirds of the chief executives of large American companies are up by 6 o’clock; for average Americans the share is less than one in three. For those aspiring to corporate greatness, the message seems clear: you snooze,…