It is one of the rituals of American capitalism. Every three months, companies, investors and analysts eagerly await the word from the corporate version of the ancient oracles: the chief executive.

Like their Greek and Roman predecessors, these corporate titans are charged with predicting the future: no number is more eagerly awaited by Wall Street than “earnings guidance” – companies’ own performance forecast. Setting a recurring target for profit growth was intended to make companies more accountable to the market and focus management minds on achieving tangible results for shareholders. But in recent months, that part of the ritual appears to be losing its appeal.