For the leaders of America Inc, high inflation is unwelcome. It is also unfamiliar. Warren Buffett, 91, the oldest boss in the s&p 500 index of big firms, last warned about the dangers of rising prices in his annual shareholder letter for 2011. The average chief executive of a company in the index, aged a mere 58, had not started university in 1979 when Paul Volcker, inflation’s enemy-in-chief, became chairman of the Federal Reserve. By the…