In an interview, Alcoa Chief Executive Klaus Kleinfeld said the “upstream” raw materials business had its best quarter since the 2008 economic slump. The aluminum company traditionally has been one of the first S&P 500 companies to report quarterly results, and some see it as a bellwether for the broader U.S. Alcoa’s stock rose 2 percent in after-hours trading to $16.42. It is up 50 percent this year, outperforming the market and aluminum prices.