Analysts are increasing sales forecasts for Standard & Poor’s 500 index companies by the most in three years, Bloomberg reported.

Revenues will climb 10 percent in 2011, twice last year’s rate, as personal income and corporate spending recover, according to analyst data. Net margin estimates were unchanged the past two months after rising more than 50 percent since 2009.

Companies that boosted profits by firing workers and closing factories in the first two years of the expansion are running out of opportunities to reduce costs, and thus need sales gains to keep growing. Though some analysts say U.S. businesses will fail to increase revenues fast enough to justify higher stock prices, some CEOs have raised forecasts.

“In the early part of the recovery, the CEO focuses on efficiency, productivity and margin enhancing, until their sales kick in,” said James Paulsen, the chief investment strategist at San Francisco-based Wells Capital Management Inc., in an interview with Bloomberg. “Once that happens, that emphasis on margins starts to fade. What looks on the surface as something you’d check off as bad is actually an indication that things are getting better.”